Deeti J. Pithadia, MD

Acute generalized pustular psoriasis (GPP) is a rare severe variant of psoriasis characterized by the sudden widespread eruption of sterile pustules.^1,2 The cutaneous manifestations of GPP also may be accompanied by signs of systemic inflammation, including fever, malaise, and leukocytosis.² Complications are common and may be life-threatening, especially in older patients with comorbid diseases.³ Generalized pustular psoriasis most commonly occurs in patients with a preceding history of psoriasis, but it also may occur de novo.⁴ Generalized pustular psoriasis is associated with notable morbidity and mortality, and relapses are common.^3,4 Many triggers of GPP have been identified, including initiation and withdrawal of various medications, infections, pregnancy, and other conditions.^5,6 Although GPP most often occurs in adults, it also may arise in children and infants.³ In pregnancy, GPP is referred to as impetigo herpetiformis, despite having no etiologic ties with either herpes simplex virus or staphylococcal or streptococcal infection. Impetigo herpetiformis is considered one of the most dangerous dermatoses of pregnancy because of high rates of associated maternal and fetal morbidity.^6,7

Acute GPP has proven to be a challenging disease to treat due to the rarity and relapsing-remitting nature of the disease; additionally, there are relatively few randomized controlled trials investigating the efficacy and safety of treatments for GPP. This review summarizes the features of GPP, including the pathophysiology of the disease, clinical and histological manifestations, and recommendations for management based on a PubMed search of articles indexed for MEDLINE using MeSH terms pertaining to the disease, including generalized pustular psoriasis, impetigo herpetiformis, and von Zumbusch psoriasis.

Pathophysiology

The pathophysiology of GPP is only partially understood, but it is thought to have a distinct pattern of immune activation compared with plaque psoriasis.⁸ Although there is a considerable amount of overlap and cross-talk among cytokine pathways, GPP generally is driven by innate immunity and unrestrained IL-36 cytokine activity. In contrast, adaptive immune responses—namely the tumor necrosis factor (TNF) α, IL-23, IL-17, and IL-22 axes—underlie plaque psoriasis.^8-10

Proinflammatory IL-36 cytokines α, β, and γ, which are all part of the IL-1 superfamily, bind to the IL-36 receptor (IL-36R) to recruit and activate immune cells via various mediators, including IL-1β; IL-8; and chemokines CXCL1, CXCL2, and CXCL8.³ The IL-36 receptor antagonist (IL-36ra) acts to inhibit this inflammatory cascade.^3,8 Microarray analyses of skin biopsy samples have shown that overexpression of IL-17A, TNF-α, IL-1, and IL-36 are seen in both GPP and plaque psoriasis lesions, but GPP lesions had higher expression of IL-1β, IL-36α, and IL-36γ and elevated neutrophil chemokines—CXCL1, CXCL2, and CXCL8—compared with plaque psoriasis lesions.⁸

Gene Mutations Associated With GPP

There are 3 gene mutations that have been associated with pustular variants of psoriasis, though these mutations account for a minority of cases of GPP.⁴ Genetic screenings are not routinely indicated in patients with GPP, but they may be warranted in severe cases when a familial pattern of inheritance is suspected.⁴

IL36RN—The gene IL36RN codes the anti-inflammatory IL-36ra. Loss-of-function mutations in IL36RN lead to impairment of IL-36ra and consequently hyperactivity of the proinflammatory responses triggered by IL-36.³ Homozygous and heterozygous mutations in IL36RN have been observed in both familial and sporadic cases of GPP.^11-13 Subsequent retrospective analyses have identified the presence of IL36RN mutations in patients with GPP with frequencies ranging from 23% to 37%.^14-17IL36RN mutations are thought to be more common in patients without concomitant plaque psoriasis and have been associated with severe disease and early disease onset.¹⁵

CARD14—A gain-of-function mutation in CARD14 results in overactivation of the proinflammatory nuclear factor κB pathway and has been implicated in cases of GPP with concurrent psoriasis vulgaris. Interestingly, this may suggest distinct etiologies underlying GPP de novo and GPP in patients with a history of psoriasis.^18,19

AP1S3—A loss-of-function mutation in AP1S3 results in abnormal endosomal trafficking and autophagy as well as increased expression of IL-36α.^20,21

Clinical Presentation and DiagnosisCutaneous Manifestations of GPP

Generalized pustular psoriasis is characterized by the onset of widespread 2- to 3-mm sterile pustules on erythematous skin or within psoriasiform plaques⁴ (Figure). In patients with skin of color, the erythema may appear less obvious or perhaps slightly violaceous compared to White skin. Pustules may coalesce to form “lakes” of pus.⁵ Cutaneous symptoms include pain, burning, and pruritus. Associated mucosal findings may include cheilitis, geographic tongue, conjunctivitis, and uveitis.⁴

The severity of symptoms can vary greatly among patients as well as between flares within the same patient.^2,3 Four distinct patterns of GPP have been described. The von Zumbusch pattern is characterized by a rapid, generalized, painful, erythematous and pustular eruption accompanied by fever and asthenia. The pustules usually resolve after several days with extensive scaling. The annular pattern is characterized by annular, erythematous, scaly lesions with pustules present centrifugally. The lesions enlarge by centrifugal expansion over a period of hours to days, while healing occurs centrally. The exanthematic type is an acute eruption of small pustules that abruptly appear and disappear within a few days, usually from infection or medication initiation. Sometimes pustules appear within or at the edge of existing psoriatic plaques in a localized pattern—the fourth pattern—often following the exposure to irritants (eg, tars, anthralin).⁵

Impetigo Herpetiformis—Impetigo herpetiformis is a form of GPP associated with pregnancy. It generally presents early in the third trimester with symmetric erythematous plaques in flexural and intertriginous areas with pustules present at lesion margins. Lesions expand centrifugally, with pustulation present at the advancing edge.^6,7 Patients often are acutely ill with fever, delirium, vomiting, and tetany. Mucous membranes, including the tongue, mouth, and esophagus, also may be involved. The eruption typically resolves after delivery, though it often recurs with subsequent pregnancies, with the morbidity risk rising with each successive pregnancy.⁷

Systemic and Extracutaneous Manifestations of GPP

Although the severity of GPP is highly variable, skin manifestations often are accompanied by systemic manifestations of inflammation, including fever and malaise. Common laboratory abnormalities include leukocytosis with peripheral neutrophilia, a high serum C-reactive protein level, hypocalcemia, and hypoalbuminemia.²² Abnormal liver enzymes often are present and result from neutrophilic cholangitis, with alternating strictures and dilations of biliary ducts observed on magnetic resonance imaging.²³ Additional laboratory abnormalities are provided in Table 2. Other extracutaneous findings associated with GPP include arthralgia, edema, and characteristic psoriatic nail changes.⁴ Fatal complications include acute respiratory distress syndrome, renal dysfunction, cardiovascular shock, and sepsis.^24,25

Histologic Features

Given the potential for the skin manifestations of GPP to mimic other disorders, a skin biopsy is warranted to confirm the diagnosis. Generalized pustular psoriasis is histologically characterized by the presence of subcorneal macropustules (ie, spongiform pustules of Kogoj) formed by neutrophil infiltration into the spongelike network of the epidermis.⁶ Otherwise, the architecture of the epithelium in GPP is similar to that seen with plaque psoriasis, with parakeratosis, acanthosis, rete-ridge elongation, diminished stratum granulosum, and thinning of the suprapapillary epidermis, though the inflammatory cell infiltrate and edema are markedly more severe in GPP than plaque psoriasis.^3,4

Differential Diagnosis

There are many other cutaneous pustular diagnoses that must be ruled out when evaluating a patient with GPP (Table 1).²⁶ Acute generalized exanthematous pustulosis (AGEP) is a common mimicker of GPP that is differentiated histologically by the presence of eosinophils and necrotic keratinocytes.⁴ In addition to its distinct histopathologic findings, AGEP is classically associated with recent initiation of certain medications, most commonly penicillins, macrolides, quinolones, sulfonamides, terbinafine, and diltiazem.²⁷ In contrast, GPP more commonly is related to withdrawal of corticosteroids as well as initiation of some biologic medications, including anti-TNF agents.³ Generalized pustular psoriasis should be suspected over AGEP in patients with a personal or family history of psoriasis, though GPP may arise in patients with or without a history of psoriasis. Acute generalized exanthematous pustulosis usually is more abrupt in both onset and resolution compared with GPP, with clearance of pustules within a few days to weeks following cessation of the triggering factor.⁴

Other pustular variants of psoriasis (eg, palmoplantar pustular psoriasis, acrodermatitis continua of Hallopeau) are differentiated from GPP by their chronicity and localization to palmoplantar and/or ungual surfaces.⁵ Other differential diagnoses are listed in Table 1.

Diagnostic Criteria for GPP

Diagnostic criteria have been proposed for GPP (Table 2), including (1) the presence of sterile pustules, (2) systemic signs of inflammation, (3) laboratory abnormalities, (4) histopathologic confirmation of spongiform pustules of Kogoj, and (5) recurrence of symptoms.²² To definitively diagnose GPP, all 5 criteria must be met. To rule out mimickers, it may be worthwhile to perform Gram staining, potassium hydroxide preparation, in vitro cultures, and/or immunofluorescence testing.⁶

Treatment

Given the high potential for mortality associated with GPP, the most essential component of management is to ensure adequate supportive care. Any temperature, fluid, or electrolyte imbalances should be corrected as they arise. Secondary infections also must be identified and treated, if present, to reduce the risk for fatal complications, including systemic infection and sepsis. Precautions must be taken to ensure that serious end-organ damage, including hepatic, renal, and respiratory dysfunction, is avoided.

Adjunctive topical intervention often is initiated with bland emollients, corticosteroids, calcineurin inhibitors, and/or vitamin D derivatives to help soothe skin symptoms, but treatment with systemic therapies usually is warranted to achieve symptom control.^2,25 Importantly, there are no systemic or topical agents that have specifically been approved for the treatment of GPP in Europe or the United States.³ Given the absence of universally accepted treatment guidelines, therapeutic agents for GPP usually are selected based on clinical experience while also taking the extent of involvement and disease severity into consideration.³

Treatment Recommendations for Adults

Oral Systemic Agents—Treatment guidelines set forth by the National Psoriasis Foundation (NPF) in 2012 proposed that first-line therapies for GPP should be acitretin, cyclosporine, methotrexate, and infliximab.²⁸ However, since those guidelines were established, many new biologic therapies have been approved for the treatment of psoriasis and often are considered in the treatment of psoriasis subtypes, including GPP.²⁹ Although retinoids previously were considered to be a preferred first-line therapy, they are associated with a high incidence of adverse effects and must be used with caution in women of childbearing age.⁶ Oral acitretin at a dosage of 0.75 to 1.0 mg/kg/d has been shown to result in clinical improvement within 1 to 2 weeks, and a maintenance dosage of 0.125 to 0.25 mg/kg/d is required for several months to prevent recurrence.³⁰ Methotrexate—5.0 to 15.0 mg/wk, or perhaps higher in patients with refractory disease, increased by 2.5-mg intervals until symptoms improve—is recommended by the NPF in patients who are unresponsive or cannot tolerate retinoids, though close monitoring for hematologic abnormalities is required. Cyclosporine 2.5 to 5.0 mg/kg/d is considered an alternative to methotrexate and retinoids; it has a faster onset of action, with improvement reported as early as 2 weeks after initiation of therapy.^1,28 Although cyclosporine may be effective in the acute phase, especially in severe cases of GPP, long-term use of cyclosporine is not recommended because of the potential for renal dysfunction and hypertension.³¹

Biologic Agents—More recent evidence has accumulated supporting the efficacy of anti-TNF agents in the treatment of GPP, suggesting the positioning of these agents as first line. A number of case series have shown dramatic and rapid improvement of GPP with intravenous infliximab 3 to 5 mg/kg, with results observed hours to days after the first infusion.^32-37 Thus, infliximab is recommended as first-line treatment in severe acute cases, though its efficacy as a maintenance therapy has not been sufficiently investigated.⁶ Case reports and case series document the safety and efficacy of adalimumab 40 to 80 mg every 1 to 2 weeks^38,39 and etanercept 25 to 50 mg twice weekly^40-42 in patients with recalcitrantGPP. Therefore, these anti-TNF agents may be considered in patients who are nonresponsive to treatment with infliximab.

Rarely, there have been reports of paradoxical induction of GPP with the use of some anti-TNF agents,^43-45 which may be due to a cytokine imbalance characterized by unopposed IFN-α activation.⁶ In patients with a history of GPP after initiation of a biologic, treatment with agents from within the offending class should be avoided.

The IL-17A monoclonal antibodies secukinumab, ixekizumab, and brodalumab have been shown in open-label phase 3 studies to result in disease remission at 12 weeks.^46-48 Treatment with guselkumab, an IL-23 monoclonal antibody, also has demonstrated efficacy in patients with GPP.⁴⁹ Ustekinumab, an IL-12/23 inhibitor, in combination with acitretin also has been shown to be successful in achieving disease remission after a few weeks of treatment.⁵⁰

More recent case reports have shown the efficacy of IL-1 inhibitors including gevokizumab, canakinumab, and anakinra in achieving GPP clearance, though more prospective studies are needed to evaluate their efficacy.^51-53 Given the etiologic association between IL-1 disinhibition and GPP, future investigations of these therapies as well as those that target the IL-36 pathway may prove to be particularly interesting.

Phototherapy and Combination Therapies—Phototherapy may be considered as maintenance therapy after disease control is achieved, though it is not considered appropriate for acute cases.²⁸ Combination therapies with a biologic plus a nonbiologic systemic agent or alternating among various biologics may allow physicians to maximize benefits and minimize adverse effects in the long term, though there is insufficient evidence to suggest any specific combination treatment algorithm for GPP.²⁸

Treatment Recommendations for Pediatric Patients

Based on a small number of case series and case reports, the first-line treatment strategy for children with GPP is similar to adults. Given the notable adverse events of most oral systemic agents, biologic therapies may emerge as first-line therapy in the pediatric population as more evidence accumulates.²⁸

Treatment Recommendations for Pregnant Patients

Systemic corticosteroids are widely considered to be the first-line treatments for the management of impetigo herpetiformis.⁷ Low-dose prednisone (15–30 mg/d) usually is effective, but severe cases may require increasing the dosage to 60 mg/d.⁶ Given the potential for rebound flares upon withdrawal of systemic corticosteroids, these agents must be gradually tapered after the resolution of symptoms.

Certolizumab pegol also is an attractive option in pregnant patients with impetigo herpetiformis because of its favorable safety profile and negligible mother-to-infant transfer through the placenta or breast milk. It has been shown to be effective in treating GPP and impetigo herpetiformis during pregnancy in recently published case reports.^54,55 In refractory cases, other TNF-α inhibitors (eg, adalimumab, infliximab, etanercept) or cyclosporine may be considered. However, cautious medical monitoring is warranted, as little is known about the potential adverse effects of these agents to the mother and fetus.^28,56 Data from transplant recipients along with several case reports indicate that cyclosporine is not associated with an increased risk for adverse effects during pregnancy at a dose of 2 to 3 mg/kg.^57-59 Both methotrexate and retinoids are known teratogens and are therefore contraindicated in pregnant patients.⁵⁶

If pustules do not resolve in the postpartum period, patients should be treated with standard GPP therapies. However, long-term and population studies are lacking regarding the potential for infant exposure to systemic agents in breast milk. Therefore, the NPF recommends avoiding breastfeeding while taking systemic medications, if possible.⁵⁶

Limitations of Treatment Recommendations

The ability to generate an evidence-based treatment strategy for GPP is limited by a lack of high-quality studies investigating the efficacy and safety of treatments in patients with GPP due to the rarity and relapsing-remitting nature of the disease, which makes randomized controlled trials difficult to conduct. The quality of the available research is further limited by the lack of validated outcome measures to specifically assess improvements in patients with GPP, such that results are difficult to synthesize and compare among studies.³¹

Conclusion

Although limited, the available research suggests that treatment with various biologics, especially infliximab, is effective in achieving rapid clearance in patients with GPP. In general, biologics may be the most appropriate treatment option in patients with GPP given their relatively favorable safety profiles. Other oral systemic agents, including acitretin, cyclosporine, and methotrexate, have limited evidence to support their use in the acute phase, but their safety profiles often limit their utility in the long-term. Emerging evidence regarding the association of GPP with IL36RN mutations suggests a unique role for agents targeting the IL-36 or IL-1 pathways, though this has yet to be thoroughly investigated.

Acute generalized pustular psoriasis (GPP) is a rare severe variant of psoriasis characterized by the sudden widespread eruption of sterile pustules.^1,2 The cutaneous manifestations of GPP also may be accompanied by signs of systemic inflammation, including fever, malaise, and leukocytosis.² Complications are common and may be life-threatening, especially in older patients with comorbid diseases.³ Generalized pustular psoriasis most commonly occurs in patients with a preceding history of psoriasis, but it also may occur de novo.⁴ Generalized pustular psoriasis is associated with notable morbidity and mortality, and relapses are common.^3,4 Many triggers of GPP have been identified, including initiation and withdrawal of various medications, infections, pregnancy, and other conditions.^5,6 Although GPP most often occurs in adults, it also may arise in children and infants.³ In pregnancy, GPP is referred to as impetigo herpetiformis, despite having no etiologic ties with either herpes simplex virus or staphylococcal or streptococcal infection. Impetigo herpetiformis is considered one of the most dangerous dermatoses of pregnancy because of high rates of associated maternal and fetal morbidity.^6,7

Acute GPP has proven to be a challenging disease to treat due to the rarity and relapsing-remitting nature of the disease; additionally, there are relatively few randomized controlled trials investigating the efficacy and safety of treatments for GPP. This review summarizes the features of GPP, including the pathophysiology of the disease, clinical and histological manifestations, and recommendations for management based on a PubMed search of articles indexed for MEDLINE using MeSH terms pertaining to the disease, including generalized pustular psoriasis, impetigo herpetiformis, and von Zumbusch psoriasis.

Pathophysiology

The pathophysiology of GPP is only partially understood, but it is thought to have a distinct pattern of immune activation compared with plaque psoriasis.⁸ Although there is a considerable amount of overlap and cross-talk among cytokine pathways, GPP generally is driven by innate immunity and unrestrained IL-36 cytokine activity. In contrast, adaptive immune responses—namely the tumor necrosis factor (TNF) α, IL-23, IL-17, and IL-22 axes—underlie plaque psoriasis.^8-10

Proinflammatory IL-36 cytokines α, β, and γ, which are all part of the IL-1 superfamily, bind to the IL-36 receptor (IL-36R) to recruit and activate immune cells via various mediators, including IL-1β; IL-8; and chemokines CXCL1, CXCL2, and CXCL8.³ The IL-36 receptor antagonist (IL-36ra) acts to inhibit this inflammatory cascade.^3,8 Microarray analyses of skin biopsy samples have shown that overexpression of IL-17A, TNF-α, IL-1, and IL-36 are seen in both GPP and plaque psoriasis lesions, but GPP lesions had higher expression of IL-1β, IL-36α, and IL-36γ and elevated neutrophil chemokines—CXCL1, CXCL2, and CXCL8—compared with plaque psoriasis lesions.⁸

Gene Mutations Associated With GPP

There are 3 gene mutations that have been associated with pustular variants of psoriasis, though these mutations account for a minority of cases of GPP.⁴ Genetic screenings are not routinely indicated in patients with GPP, but they may be warranted in severe cases when a familial pattern of inheritance is suspected.⁴

IL36RN—The gene IL36RN codes the anti-inflammatory IL-36ra. Loss-of-function mutations in IL36RN lead to impairment of IL-36ra and consequently hyperactivity of the proinflammatory responses triggered by IL-36.³ Homozygous and heterozygous mutations in IL36RN have been observed in both familial and sporadic cases of GPP.^11-13 Subsequent retrospective analyses have identified the presence of IL36RN mutations in patients with GPP with frequencies ranging from 23% to 37%.^14-17IL36RN mutations are thought to be more common in patients without concomitant plaque psoriasis and have been associated with severe disease and early disease onset.¹⁵

CARD14—A gain-of-function mutation in CARD14 results in overactivation of the proinflammatory nuclear factor κB pathway and has been implicated in cases of GPP with concurrent psoriasis vulgaris. Interestingly, this may suggest distinct etiologies underlying GPP de novo and GPP in patients with a history of psoriasis.^18,19

AP1S3—A loss-of-function mutation in AP1S3 results in abnormal endosomal trafficking and autophagy as well as increased expression of IL-36α.^20,21

Clinical Presentation and DiagnosisCutaneous Manifestations of GPP

Generalized pustular psoriasis is characterized by the onset of widespread 2- to 3-mm sterile pustules on erythematous skin or within psoriasiform plaques⁴ (Figure). In patients with skin of color, the erythema may appear less obvious or perhaps slightly violaceous compared to White skin. Pustules may coalesce to form “lakes” of pus.⁵ Cutaneous symptoms include pain, burning, and pruritus. Associated mucosal findings may include cheilitis, geographic tongue, conjunctivitis, and uveitis.⁴

The severity of symptoms can vary greatly among patients as well as between flares within the same patient.^2,3 Four distinct patterns of GPP have been described. The von Zumbusch pattern is characterized by a rapid, generalized, painful, erythematous and pustular eruption accompanied by fever and asthenia. The pustules usually resolve after several days with extensive scaling. The annular pattern is characterized by annular, erythematous, scaly lesions with pustules present centrifugally. The lesions enlarge by centrifugal expansion over a period of hours to days, while healing occurs centrally. The exanthematic type is an acute eruption of small pustules that abruptly appear and disappear within a few days, usually from infection or medication initiation. Sometimes pustules appear within or at the edge of existing psoriatic plaques in a localized pattern—the fourth pattern—often following the exposure to irritants (eg, tars, anthralin).⁵

Impetigo Herpetiformis—Impetigo herpetiformis is a form of GPP associated with pregnancy. It generally presents early in the third trimester with symmetric erythematous plaques in flexural and intertriginous areas with pustules present at lesion margins. Lesions expand centrifugally, with pustulation present at the advancing edge.^6,7 Patients often are acutely ill with fever, delirium, vomiting, and tetany. Mucous membranes, including the tongue, mouth, and esophagus, also may be involved. The eruption typically resolves after delivery, though it often recurs with subsequent pregnancies, with the morbidity risk rising with each successive pregnancy.⁷

Systemic and Extracutaneous Manifestations of GPP

Although the severity of GPP is highly variable, skin manifestations often are accompanied by systemic manifestations of inflammation, including fever and malaise. Common laboratory abnormalities include leukocytosis with peripheral neutrophilia, a high serum C-reactive protein level, hypocalcemia, and hypoalbuminemia.²² Abnormal liver enzymes often are present and result from neutrophilic cholangitis, with alternating strictures and dilations of biliary ducts observed on magnetic resonance imaging.²³ Additional laboratory abnormalities are provided in Table 2. Other extracutaneous findings associated with GPP include arthralgia, edema, and characteristic psoriatic nail changes.⁴ Fatal complications include acute respiratory distress syndrome, renal dysfunction, cardiovascular shock, and sepsis.^24,25

Histologic Features

Given the potential for the skin manifestations of GPP to mimic other disorders, a skin biopsy is warranted to confirm the diagnosis. Generalized pustular psoriasis is histologically characterized by the presence of subcorneal macropustules (ie, spongiform pustules of Kogoj) formed by neutrophil infiltration into the spongelike network of the epidermis.⁶ Otherwise, the architecture of the epithelium in GPP is similar to that seen with plaque psoriasis, with parakeratosis, acanthosis, rete-ridge elongation, diminished stratum granulosum, and thinning of the suprapapillary epidermis, though the inflammatory cell infiltrate and edema are markedly more severe in GPP than plaque psoriasis.^3,4

Differential Diagnosis

There are many other cutaneous pustular diagnoses that must be ruled out when evaluating a patient with GPP (Table 1).²⁶ Acute generalized exanthematous pustulosis (AGEP) is a common mimicker of GPP that is differentiated histologically by the presence of eosinophils and necrotic keratinocytes.⁴ In addition to its distinct histopathologic findings, AGEP is classically associated with recent initiation of certain medications, most commonly penicillins, macrolides, quinolones, sulfonamides, terbinafine, and diltiazem.²⁷ In contrast, GPP more commonly is related to withdrawal of corticosteroids as well as initiation of some biologic medications, including anti-TNF agents.³ Generalized pustular psoriasis should be suspected over AGEP in patients with a personal or family history of psoriasis, though GPP may arise in patients with or without a history of psoriasis. Acute generalized exanthematous pustulosis usually is more abrupt in both onset and resolution compared with GPP, with clearance of pustules within a few days to weeks following cessation of the triggering factor.⁴

Other pustular variants of psoriasis (eg, palmoplantar pustular psoriasis, acrodermatitis continua of Hallopeau) are differentiated from GPP by their chronicity and localization to palmoplantar and/or ungual surfaces.⁵ Other differential diagnoses are listed in Table 1.

Diagnostic Criteria for GPP

Diagnostic criteria have been proposed for GPP (Table 2), including (1) the presence of sterile pustules, (2) systemic signs of inflammation, (3) laboratory abnormalities, (4) histopathologic confirmation of spongiform pustules of Kogoj, and (5) recurrence of symptoms.²² To definitively diagnose GPP, all 5 criteria must be met. To rule out mimickers, it may be worthwhile to perform Gram staining, potassium hydroxide preparation, in vitro cultures, and/or immunofluorescence testing.⁶

Treatment

Given the high potential for mortality associated with GPP, the most essential component of management is to ensure adequate supportive care. Any temperature, fluid, or electrolyte imbalances should be corrected as they arise. Secondary infections also must be identified and treated, if present, to reduce the risk for fatal complications, including systemic infection and sepsis. Precautions must be taken to ensure that serious end-organ damage, including hepatic, renal, and respiratory dysfunction, is avoided.

Adjunctive topical intervention often is initiated with bland emollients, corticosteroids, calcineurin inhibitors, and/or vitamin D derivatives to help soothe skin symptoms, but treatment with systemic therapies usually is warranted to achieve symptom control.^2,25 Importantly, there are no systemic or topical agents that have specifically been approved for the treatment of GPP in Europe or the United States.³ Given the absence of universally accepted treatment guidelines, therapeutic agents for GPP usually are selected based on clinical experience while also taking the extent of involvement and disease severity into consideration.³

Treatment Recommendations for Adults

Oral Systemic Agents—Treatment guidelines set forth by the National Psoriasis Foundation (NPF) in 2012 proposed that first-line therapies for GPP should be acitretin, cyclosporine, methotrexate, and infliximab.²⁸ However, since those guidelines were established, many new biologic therapies have been approved for the treatment of psoriasis and often are considered in the treatment of psoriasis subtypes, including GPP.²⁹ Although retinoids previously were considered to be a preferred first-line therapy, they are associated with a high incidence of adverse effects and must be used with caution in women of childbearing age.⁶ Oral acitretin at a dosage of 0.75 to 1.0 mg/kg/d has been shown to result in clinical improvement within 1 to 2 weeks, and a maintenance dosage of 0.125 to 0.25 mg/kg/d is required for several months to prevent recurrence.³⁰ Methotrexate—5.0 to 15.0 mg/wk, or perhaps higher in patients with refractory disease, increased by 2.5-mg intervals until symptoms improve—is recommended by the NPF in patients who are unresponsive or cannot tolerate retinoids, though close monitoring for hematologic abnormalities is required. Cyclosporine 2.5 to 5.0 mg/kg/d is considered an alternative to methotrexate and retinoids; it has a faster onset of action, with improvement reported as early as 2 weeks after initiation of therapy.^1,28 Although cyclosporine may be effective in the acute phase, especially in severe cases of GPP, long-term use of cyclosporine is not recommended because of the potential for renal dysfunction and hypertension.³¹

Biologic Agents—More recent evidence has accumulated supporting the efficacy of anti-TNF agents in the treatment of GPP, suggesting the positioning of these agents as first line. A number of case series have shown dramatic and rapid improvement of GPP with intravenous infliximab 3 to 5 mg/kg, with results observed hours to days after the first infusion.^32-37 Thus, infliximab is recommended as first-line treatment in severe acute cases, though its efficacy as a maintenance therapy has not been sufficiently investigated.⁶ Case reports and case series document the safety and efficacy of adalimumab 40 to 80 mg every 1 to 2 weeks^38,39 and etanercept 25 to 50 mg twice weekly^40-42 in patients with recalcitrantGPP. Therefore, these anti-TNF agents may be considered in patients who are nonresponsive to treatment with infliximab.

Rarely, there have been reports of paradoxical induction of GPP with the use of some anti-TNF agents,^43-45 which may be due to a cytokine imbalance characterized by unopposed IFN-α activation.⁶ In patients with a history of GPP after initiation of a biologic, treatment with agents from within the offending class should be avoided.

The IL-17A monoclonal antibodies secukinumab, ixekizumab, and brodalumab have been shown in open-label phase 3 studies to result in disease remission at 12 weeks.^46-48 Treatment with guselkumab, an IL-23 monoclonal antibody, also has demonstrated efficacy in patients with GPP.⁴⁹ Ustekinumab, an IL-12/23 inhibitor, in combination with acitretin also has been shown to be successful in achieving disease remission after a few weeks of treatment.⁵⁰

More recent case reports have shown the efficacy of IL-1 inhibitors including gevokizumab, canakinumab, and anakinra in achieving GPP clearance, though more prospective studies are needed to evaluate their efficacy.^51-53 Given the etiologic association between IL-1 disinhibition and GPP, future investigations of these therapies as well as those that target the IL-36 pathway may prove to be particularly interesting.

Phototherapy and Combination Therapies—Phototherapy may be considered as maintenance therapy after disease control is achieved, though it is not considered appropriate for acute cases.²⁸ Combination therapies with a biologic plus a nonbiologic systemic agent or alternating among various biologics may allow physicians to maximize benefits and minimize adverse effects in the long term, though there is insufficient evidence to suggest any specific combination treatment algorithm for GPP.²⁸

Treatment Recommendations for Pediatric Patients

Based on a small number of case series and case reports, the first-line treatment strategy for children with GPP is similar to adults. Given the notable adverse events of most oral systemic agents, biologic therapies may emerge as first-line therapy in the pediatric population as more evidence accumulates.²⁸

Treatment Recommendations for Pregnant Patients

Systemic corticosteroids are widely considered to be the first-line treatments for the management of impetigo herpetiformis.⁷ Low-dose prednisone (15–30 mg/d) usually is effective, but severe cases may require increasing the dosage to 60 mg/d.⁶ Given the potential for rebound flares upon withdrawal of systemic corticosteroids, these agents must be gradually tapered after the resolution of symptoms.

Certolizumab pegol also is an attractive option in pregnant patients with impetigo herpetiformis because of its favorable safety profile and negligible mother-to-infant transfer through the placenta or breast milk. It has been shown to be effective in treating GPP and impetigo herpetiformis during pregnancy in recently published case reports.^54,55 In refractory cases, other TNF-α inhibitors (eg, adalimumab, infliximab, etanercept) or cyclosporine may be considered. However, cautious medical monitoring is warranted, as little is known about the potential adverse effects of these agents to the mother and fetus.^28,56 Data from transplant recipients along with several case reports indicate that cyclosporine is not associated with an increased risk for adverse effects during pregnancy at a dose of 2 to 3 mg/kg.^57-59 Both methotrexate and retinoids are known teratogens and are therefore contraindicated in pregnant patients.⁵⁶

If pustules do not resolve in the postpartum period, patients should be treated with standard GPP therapies. However, long-term and population studies are lacking regarding the potential for infant exposure to systemic agents in breast milk. Therefore, the NPF recommends avoiding breastfeeding while taking systemic medications, if possible.⁵⁶

Limitations of Treatment Recommendations

The ability to generate an evidence-based treatment strategy for GPP is limited by a lack of high-quality studies investigating the efficacy and safety of treatments in patients with GPP due to the rarity and relapsing-remitting nature of the disease, which makes randomized controlled trials difficult to conduct. The quality of the available research is further limited by the lack of validated outcome measures to specifically assess improvements in patients with GPP, such that results are difficult to synthesize and compare among studies.³¹

Conclusion

Although limited, the available research suggests that treatment with various biologics, especially infliximab, is effective in achieving rapid clearance in patients with GPP. In general, biologics may be the most appropriate treatment option in patients with GPP given their relatively favorable safety profiles. Other oral systemic agents, including acitretin, cyclosporine, and methotrexate, have limited evidence to support their use in the acute phase, but their safety profiles often limit their utility in the long-term. Emerging evidence regarding the association of GPP with IL36RN mutations suggests a unique role for agents targeting the IL-36 or IL-1 pathways, though this has yet to be thoroughly investigated.

Acute generalized pustular psoriasis (GPP) is a rare severe variant of psoriasis characterized by the sudden widespread eruption of sterile pustules.^1,2 The cutaneous manifestations of GPP also may be accompanied by signs of systemic inflammation, including fever, malaise, and leukocytosis.² Complications are common and may be life-threatening, especially in older patients with comorbid diseases.³ Generalized pustular psoriasis most commonly occurs in patients with a preceding history of psoriasis, but it also may occur de novo.⁴ Generalized pustular psoriasis is associated with notable morbidity and mortality, and relapses are common.^3,4 Many triggers of GPP have been identified, including initiation and withdrawal of various medications, infections, pregnancy, and other conditions.^5,6 Although GPP most often occurs in adults, it also may arise in children and infants.³ In pregnancy, GPP is referred to as impetigo herpetiformis, despite having no etiologic ties with either herpes simplex virus or staphylococcal or streptococcal infection. Impetigo herpetiformis is considered one of the most dangerous dermatoses of pregnancy because of high rates of associated maternal and fetal morbidity.^6,7

Acute GPP has proven to be a challenging disease to treat due to the rarity and relapsing-remitting nature of the disease; additionally, there are relatively few randomized controlled trials investigating the efficacy and safety of treatments for GPP. This review summarizes the features of GPP, including the pathophysiology of the disease, clinical and histological manifestations, and recommendations for management based on a PubMed search of articles indexed for MEDLINE using MeSH terms pertaining to the disease, including generalized pustular psoriasis, impetigo herpetiformis, and von Zumbusch psoriasis.

Pathophysiology

The pathophysiology of GPP is only partially understood, but it is thought to have a distinct pattern of immune activation compared with plaque psoriasis.⁸ Although there is a considerable amount of overlap and cross-talk among cytokine pathways, GPP generally is driven by innate immunity and unrestrained IL-36 cytokine activity. In contrast, adaptive immune responses—namely the tumor necrosis factor (TNF) α, IL-23, IL-17, and IL-22 axes—underlie plaque psoriasis.^8-10

Proinflammatory IL-36 cytokines α, β, and γ, which are all part of the IL-1 superfamily, bind to the IL-36 receptor (IL-36R) to recruit and activate immune cells via various mediators, including IL-1β; IL-8; and chemokines CXCL1, CXCL2, and CXCL8.³ The IL-36 receptor antagonist (IL-36ra) acts to inhibit this inflammatory cascade.^3,8 Microarray analyses of skin biopsy samples have shown that overexpression of IL-17A, TNF-α, IL-1, and IL-36 are seen in both GPP and plaque psoriasis lesions, but GPP lesions had higher expression of IL-1β, IL-36α, and IL-36γ and elevated neutrophil chemokines—CXCL1, CXCL2, and CXCL8—compared with plaque psoriasis lesions.⁸

Gene Mutations Associated With GPP

There are 3 gene mutations that have been associated with pustular variants of psoriasis, though these mutations account for a minority of cases of GPP.⁴ Genetic screenings are not routinely indicated in patients with GPP, but they may be warranted in severe cases when a familial pattern of inheritance is suspected.⁴

IL36RN—The gene IL36RN codes the anti-inflammatory IL-36ra. Loss-of-function mutations in IL36RN lead to impairment of IL-36ra and consequently hyperactivity of the proinflammatory responses triggered by IL-36.³ Homozygous and heterozygous mutations in IL36RN have been observed in both familial and sporadic cases of GPP.^11-13 Subsequent retrospective analyses have identified the presence of IL36RN mutations in patients with GPP with frequencies ranging from 23% to 37%.^14-17IL36RN mutations are thought to be more common in patients without concomitant plaque psoriasis and have been associated with severe disease and early disease onset.¹⁵

CARD14—A gain-of-function mutation in CARD14 results in overactivation of the proinflammatory nuclear factor κB pathway and has been implicated in cases of GPP with concurrent psoriasis vulgaris. Interestingly, this may suggest distinct etiologies underlying GPP de novo and GPP in patients with a history of psoriasis.^18,19

AP1S3—A loss-of-function mutation in AP1S3 results in abnormal endosomal trafficking and autophagy as well as increased expression of IL-36α.^20,21

Clinical Presentation and DiagnosisCutaneous Manifestations of GPP

Generalized pustular psoriasis is characterized by the onset of widespread 2- to 3-mm sterile pustules on erythematous skin or within psoriasiform plaques⁴ (Figure). In patients with skin of color, the erythema may appear less obvious or perhaps slightly violaceous compared to White skin. Pustules may coalesce to form “lakes” of pus.⁵ Cutaneous symptoms include pain, burning, and pruritus. Associated mucosal findings may include cheilitis, geographic tongue, conjunctivitis, and uveitis.⁴

The severity of symptoms can vary greatly among patients as well as between flares within the same patient.^2,3 Four distinct patterns of GPP have been described. The von Zumbusch pattern is characterized by a rapid, generalized, painful, erythematous and pustular eruption accompanied by fever and asthenia. The pustules usually resolve after several days with extensive scaling. The annular pattern is characterized by annular, erythematous, scaly lesions with pustules present centrifugally. The lesions enlarge by centrifugal expansion over a period of hours to days, while healing occurs centrally. The exanthematic type is an acute eruption of small pustules that abruptly appear and disappear within a few days, usually from infection or medication initiation. Sometimes pustules appear within or at the edge of existing psoriatic plaques in a localized pattern—the fourth pattern—often following the exposure to irritants (eg, tars, anthralin).⁵

Impetigo Herpetiformis—Impetigo herpetiformis is a form of GPP associated with pregnancy. It generally presents early in the third trimester with symmetric erythematous plaques in flexural and intertriginous areas with pustules present at lesion margins. Lesions expand centrifugally, with pustulation present at the advancing edge.^6,7 Patients often are acutely ill with fever, delirium, vomiting, and tetany. Mucous membranes, including the tongue, mouth, and esophagus, also may be involved. The eruption typically resolves after delivery, though it often recurs with subsequent pregnancies, with the morbidity risk rising with each successive pregnancy.⁷

Systemic and Extracutaneous Manifestations of GPP

Although the severity of GPP is highly variable, skin manifestations often are accompanied by systemic manifestations of inflammation, including fever and malaise. Common laboratory abnormalities include leukocytosis with peripheral neutrophilia, a high serum C-reactive protein level, hypocalcemia, and hypoalbuminemia.²² Abnormal liver enzymes often are present and result from neutrophilic cholangitis, with alternating strictures and dilations of biliary ducts observed on magnetic resonance imaging.²³ Additional laboratory abnormalities are provided in Table 2. Other extracutaneous findings associated with GPP include arthralgia, edema, and characteristic psoriatic nail changes.⁴ Fatal complications include acute respiratory distress syndrome, renal dysfunction, cardiovascular shock, and sepsis.^24,25

Histologic Features

Given the potential for the skin manifestations of GPP to mimic other disorders, a skin biopsy is warranted to confirm the diagnosis. Generalized pustular psoriasis is histologically characterized by the presence of subcorneal macropustules (ie, spongiform pustules of Kogoj) formed by neutrophil infiltration into the spongelike network of the epidermis.⁶ Otherwise, the architecture of the epithelium in GPP is similar to that seen with plaque psoriasis, with parakeratosis, acanthosis, rete-ridge elongation, diminished stratum granulosum, and thinning of the suprapapillary epidermis, though the inflammatory cell infiltrate and edema are markedly more severe in GPP than plaque psoriasis.^3,4

Differential Diagnosis

There are many other cutaneous pustular diagnoses that must be ruled out when evaluating a patient with GPP (Table 1).²⁶ Acute generalized exanthematous pustulosis (AGEP) is a common mimicker of GPP that is differentiated histologically by the presence of eosinophils and necrotic keratinocytes.⁴ In addition to its distinct histopathologic findings, AGEP is classically associated with recent initiation of certain medications, most commonly penicillins, macrolides, quinolones, sulfonamides, terbinafine, and diltiazem.²⁷ In contrast, GPP more commonly is related to withdrawal of corticosteroids as well as initiation of some biologic medications, including anti-TNF agents.³ Generalized pustular psoriasis should be suspected over AGEP in patients with a personal or family history of psoriasis, though GPP may arise in patients with or without a history of psoriasis. Acute generalized exanthematous pustulosis usually is more abrupt in both onset and resolution compared with GPP, with clearance of pustules within a few days to weeks following cessation of the triggering factor.⁴

Other pustular variants of psoriasis (eg, palmoplantar pustular psoriasis, acrodermatitis continua of Hallopeau) are differentiated from GPP by their chronicity and localization to palmoplantar and/or ungual surfaces.⁵ Other differential diagnoses are listed in Table 1.

Diagnostic Criteria for GPP

Diagnostic criteria have been proposed for GPP (Table 2), including (1) the presence of sterile pustules, (2) systemic signs of inflammation, (3) laboratory abnormalities, (4) histopathologic confirmation of spongiform pustules of Kogoj, and (5) recurrence of symptoms.²² To definitively diagnose GPP, all 5 criteria must be met. To rule out mimickers, it may be worthwhile to perform Gram staining, potassium hydroxide preparation, in vitro cultures, and/or immunofluorescence testing.⁶

Treatment

Given the high potential for mortality associated with GPP, the most essential component of management is to ensure adequate supportive care. Any temperature, fluid, or electrolyte imbalances should be corrected as they arise. Secondary infections also must be identified and treated, if present, to reduce the risk for fatal complications, including systemic infection and sepsis. Precautions must be taken to ensure that serious end-organ damage, including hepatic, renal, and respiratory dysfunction, is avoided.

Adjunctive topical intervention often is initiated with bland emollients, corticosteroids, calcineurin inhibitors, and/or vitamin D derivatives to help soothe skin symptoms, but treatment with systemic therapies usually is warranted to achieve symptom control.^2,25 Importantly, there are no systemic or topical agents that have specifically been approved for the treatment of GPP in Europe or the United States.³ Given the absence of universally accepted treatment guidelines, therapeutic agents for GPP usually are selected based on clinical experience while also taking the extent of involvement and disease severity into consideration.³

Treatment Recommendations for Adults

Oral Systemic Agents—Treatment guidelines set forth by the National Psoriasis Foundation (NPF) in 2012 proposed that first-line therapies for GPP should be acitretin, cyclosporine, methotrexate, and infliximab.²⁸ However, since those guidelines were established, many new biologic therapies have been approved for the treatment of psoriasis and often are considered in the treatment of psoriasis subtypes, including GPP.²⁹ Although retinoids previously were considered to be a preferred first-line therapy, they are associated with a high incidence of adverse effects and must be used with caution in women of childbearing age.⁶ Oral acitretin at a dosage of 0.75 to 1.0 mg/kg/d has been shown to result in clinical improvement within 1 to 2 weeks, and a maintenance dosage of 0.125 to 0.25 mg/kg/d is required for several months to prevent recurrence.³⁰ Methotrexate—5.0 to 15.0 mg/wk, or perhaps higher in patients with refractory disease, increased by 2.5-mg intervals until symptoms improve—is recommended by the NPF in patients who are unresponsive or cannot tolerate retinoids, though close monitoring for hematologic abnormalities is required. Cyclosporine 2.5 to 5.0 mg/kg/d is considered an alternative to methotrexate and retinoids; it has a faster onset of action, with improvement reported as early as 2 weeks after initiation of therapy.^1,28 Although cyclosporine may be effective in the acute phase, especially in severe cases of GPP, long-term use of cyclosporine is not recommended because of the potential for renal dysfunction and hypertension.³¹

Biologic Agents—More recent evidence has accumulated supporting the efficacy of anti-TNF agents in the treatment of GPP, suggesting the positioning of these agents as first line. A number of case series have shown dramatic and rapid improvement of GPP with intravenous infliximab 3 to 5 mg/kg, with results observed hours to days after the first infusion.^32-37 Thus, infliximab is recommended as first-line treatment in severe acute cases, though its efficacy as a maintenance therapy has not been sufficiently investigated.⁶ Case reports and case series document the safety and efficacy of adalimumab 40 to 80 mg every 1 to 2 weeks^38,39 and etanercept 25 to 50 mg twice weekly^40-42 in patients with recalcitrantGPP. Therefore, these anti-TNF agents may be considered in patients who are nonresponsive to treatment with infliximab.

Rarely, there have been reports of paradoxical induction of GPP with the use of some anti-TNF agents,^43-45 which may be due to a cytokine imbalance characterized by unopposed IFN-α activation.⁶ In patients with a history of GPP after initiation of a biologic, treatment with agents from within the offending class should be avoided.

The IL-17A monoclonal antibodies secukinumab, ixekizumab, and brodalumab have been shown in open-label phase 3 studies to result in disease remission at 12 weeks.^46-48 Treatment with guselkumab, an IL-23 monoclonal antibody, also has demonstrated efficacy in patients with GPP.⁴⁹ Ustekinumab, an IL-12/23 inhibitor, in combination with acitretin also has been shown to be successful in achieving disease remission after a few weeks of treatment.⁵⁰

More recent case reports have shown the efficacy of IL-1 inhibitors including gevokizumab, canakinumab, and anakinra in achieving GPP clearance, though more prospective studies are needed to evaluate their efficacy.^51-53 Given the etiologic association between IL-1 disinhibition and GPP, future investigations of these therapies as well as those that target the IL-36 pathway may prove to be particularly interesting.

Phototherapy and Combination Therapies—Phototherapy may be considered as maintenance therapy after disease control is achieved, though it is not considered appropriate for acute cases.²⁸ Combination therapies with a biologic plus a nonbiologic systemic agent or alternating among various biologics may allow physicians to maximize benefits and minimize adverse effects in the long term, though there is insufficient evidence to suggest any specific combination treatment algorithm for GPP.²⁸

Treatment Recommendations for Pediatric Patients

Based on a small number of case series and case reports, the first-line treatment strategy for children with GPP is similar to adults. Given the notable adverse events of most oral systemic agents, biologic therapies may emerge as first-line therapy in the pediatric population as more evidence accumulates.²⁸

Treatment Recommendations for Pregnant Patients

Systemic corticosteroids are widely considered to be the first-line treatments for the management of impetigo herpetiformis.⁷ Low-dose prednisone (15–30 mg/d) usually is effective, but severe cases may require increasing the dosage to 60 mg/d.⁶ Given the potential for rebound flares upon withdrawal of systemic corticosteroids, these agents must be gradually tapered after the resolution of symptoms.

Certolizumab pegol also is an attractive option in pregnant patients with impetigo herpetiformis because of its favorable safety profile and negligible mother-to-infant transfer through the placenta or breast milk. It has been shown to be effective in treating GPP and impetigo herpetiformis during pregnancy in recently published case reports.^54,55 In refractory cases, other TNF-α inhibitors (eg, adalimumab, infliximab, etanercept) or cyclosporine may be considered. However, cautious medical monitoring is warranted, as little is known about the potential adverse effects of these agents to the mother and fetus.^28,56 Data from transplant recipients along with several case reports indicate that cyclosporine is not associated with an increased risk for adverse effects during pregnancy at a dose of 2 to 3 mg/kg.^57-59 Both methotrexate and retinoids are known teratogens and are therefore contraindicated in pregnant patients.⁵⁶

If pustules do not resolve in the postpartum period, patients should be treated with standard GPP therapies. However, long-term and population studies are lacking regarding the potential for infant exposure to systemic agents in breast milk. Therefore, the NPF recommends avoiding breastfeeding while taking systemic medications, if possible.⁵⁶

Limitations of Treatment Recommendations

The ability to generate an evidence-based treatment strategy for GPP is limited by a lack of high-quality studies investigating the efficacy and safety of treatments in patients with GPP due to the rarity and relapsing-remitting nature of the disease, which makes randomized controlled trials difficult to conduct. The quality of the available research is further limited by the lack of validated outcome measures to specifically assess improvements in patients with GPP, such that results are difficult to synthesize and compare among studies.³¹

Conclusion

Although limited, the available research suggests that treatment with various biologics, especially infliximab, is effective in achieving rapid clearance in patients with GPP. In general, biologics may be the most appropriate treatment option in patients with GPP given their relatively favorable safety profiles. Other oral systemic agents, including acitretin, cyclosporine, and methotrexate, have limited evidence to support their use in the acute phase, but their safety profiles often limit their utility in the long-term. Emerging evidence regarding the association of GPP with IL36RN mutations suggests a unique role for agents targeting the IL-36 or IL-1 pathways, though this has yet to be thoroughly investigated.

In November 2019, the American Academy of Dermatology (AAD) and the National Psoriasis Foundation (NPF) released their first set of recommendations for the management of pediatric psoriasis.¹ The pediatric guidelines discuss methods of quantifying disease severity in children, triggers and comorbidities, and the efficacy and safety of various therapeutic agents. This review aims to discuss, in a condensed form, special considerations unique to the management of children with psoriasis as presented in the guidelines as well as grade A– and grade B–level treatment recommendations (Table).

Quantifying Psoriasis Severity in Children

Percentage body surface area (BSA) involvement is the most common mode of grading psoriasis severity, with less than 3% BSA involvement being considered mild, 3% to 10% BSA moderate, and more than 10% severe disease. In children, the standard method of measuring BSA is the rule of 9’s: the head and each arm make up 9% of the total BSA, each leg and the front and back of the torso respectively each make up 18%, and the genitalia make up 1%. It also is important to consider impact on quality of life, which may be remarkable in spite of limited BSA involvement. The children’s dermatology life quality index score may be utilized in combination with affected BSA to determine the burden of psoriasis in context of impact on daily life. This metric is available in both written and cartoon form, and it consists of 10 questions that include variables such as severity of itch, impact on social life, and effects on sleep. Most notably, this tool incorporates pruritus,² which generally is addressed inadequately in pediatric psoriasis.

Triggers and Comorbidities in Pediatric Patients

In children, it is important to identify and eliminate modifiable factors that may prompt psoriasis flares. Infections, particularly group A beta-hemolytic streptococcal infections, are a major trigger in neonates and infants. Other exacerbating factors in children include emotional stress, secondhand cigarette smoke, Kawasaki disease, and withdrawal from systemic corticosteroids.

Psoriatic arthritis (PsA) is a burdensome comorbidity affecting children with psoriasis. The prevalence of joint disease is 15-times greater in children with psoriasis vs those without,³ and 80% of children with PsA develop rheumatologic symptoms, which typically include oligoarticular disease and dactylitis in infants and girls and enthesitis and axial joint involvement in boys and older children, years prior to the onset of cutaneous disease.⁴ Uveitis often occurs in children with psoriasis and PsA but not in those with isolated cutaneous disease.

Compared to unaffected children, pediatric patients with psoriasis have greater prevalence of metabolic and cardiovascular risk factors during childhood, including central obesity, hypertension, hypertriglyceridemia, hypercholesterolemia, insulin resistance, atherosclerosis, arrythmia, and valvular heart disease. Family history of obesity increases the risk for early-onset development of cutaneous lesions,^5,6 and weight reduction may alleviate severity of psoriasis lesions.⁷ In the United States, many of the metabolic associations observed are particularly robust in Black and Hispanic children vs those of other races. Furthermore, the prevalence of inflammatory bowel disease is 3- to 4-times higher in children with psoriasis compared to those without.

As with other cutaneous diseases, it is important to be aware of social and mental health concerns in children with psoriasis. The majority of pediatric patients with psoriasis experience name-calling, shaming, or bullying, and many have concerns from skin shedding and malodor. Independent risk for depression after the onset of psoriasis is high. Affected older children and adolescents are at increased risk for alcohol and drug abuse as well as eating disorders.

Despite these identified comorbidities, there are no unique screening recommendations for arthritis, ophthalmologic disease, metabolic disease, cardiovascular disease, gastrointestinal tract disease, or mental health issues in children with psoriasis. Rather, these patients should be monitored according to the American Academy of Pediatrics or American Diabetes Association guidelines for all pediatric patients.^8,9 Nonetheless, educating patients and guardians about these potential issues may be warranted.

Topical Therapies

For children with mild to moderate psoriasis, topical therapies are first line. Despite being off label, topical corticosteroids are the mainstay of therapy for localized psoriatic plaques in children. Topical vitamin D analogues—calcitriol and calcipotriol/calcipotriene—are highly effective and well tolerated, and they frequently are used in combination with topical corticosteroids. Topical calcineurin inhibitors, namely tacrolimus, also are used off label but are considered first line for sensitive regions of the skin in children, including the face, genitalia, and body folds. There currently is limited evidence for supporting the use of the topical vitamin A analogue tazarotene in children with psoriasis, though some consider its off-label use effective for pediatric nail psoriasis. It also may be used as an adjunct to topical corticosteroids to minimize irritation.

Although there is no gold standard topical regimen, combination therapy with a high-potency topical steroid and topical vitamin D analogue commonly is used to minimize steroid-induced side effects. For the first 2 weeks of treatment, they each may be applied once daily or mixed together and applied twice daily. For subsequent maintenance, topical calcipotriene may be applied on weekdays and topical steroids only on weekends. Combination calcipotriol–betamethasone dipropionate also is available as cream, ointment, foam, and suspension vehicles for use on the body and scalp in children aged 12 years and older. Tacrolimus ointment 0.1% may be applied in a thin layer up to twice daily. Concurrent emollient use also is recommended with these therapies.

Health care providers should educate patients and guardians about the potential side effects of topical therapies. They also should provide explicit instructions for amount, site, frequency, and duration of application. Topical corticosteroids commonly result in burning on application and may potentially cause skin thinning and striae with overuse. Topical vitamin D analogues may result in local irritation that may be improved by concurrent emollient use, and they generally should be avoided on sensitive sites. Topical calcineurin inhibitors are associated with burning, stinging, and pruritus, and the US Food and Drug Administration has issued a black-box warning related to risk for lymphoma with their chronic intermittent use. However, it was based on rare reports of lymphoma in transplant patients taking oral calcineurin inhibitors; no clinical trials to date in humans have demonstrated an increased risk for malignancy with topical calcineurin inhibitors.¹⁰ Tazarotene should be used cautiously in females of childbearing age given its teratogenic potential.

Children younger than 7 years are especially prone to suppression of the hypothalamic-pituitary-adrenal axis from topical corticosteroid therapy and theoretically hypercalcemia and hypervitaminosis D from topical vitamin D analogues, as their high BSA-to-volume ratio increases potential for systemic absorption. Children should avoid occlusive application of topical vitamin D analogues to large areas of the skin. Monitoring of vitamin D metabolites in the serum may be considered if calcipotriene or calcipotriol application to a large BSA is warranted.

Light-Based Therapy

In children with widespread psoriasis or those refractory to topical therapy, phototherapy may be considered. Narrowband UVB (311- to 313-nm wavelength) therapy is considered a first-line form of phototherapy in pediatric psoriasis. Mineral oil or emollient pretreatment to affected areas may augment the efficacy of UV-based treatments.¹¹ Excimer laser and UVA also may be efficacious, though evidence is limited in children. Treatment is recommended to start at 3 days a week, and once improvement is seen, the frequency can be decreased to 2 days a week. Once desired clearance is achieved, maintenance therapy can be continued at even longer intervals. Adjunctive use of tar preparations may potentiate the efficacy of phototherapy, though there is a theoretical increased risk for carcinogenicity with prolonged use of coal tar. Side effects of phototherapy include erythema, blistering hyperpigmentation, and pruritus. Psoralen is contraindicated in children younger than 12 years. All forms of phototherapy are contraindicated in children with generalized erythroderma and cutaneous cancer syndromes. Other important pediatric-specific considerations include anxiety that may be provoked by UV light machines and inconvenience of frequent appointments.

Nonbiologic Systemic Therapies

Systemic therapies may be considered in children with recalcitrant, widespread, or rapidly progressing psoriasis, particularly if the disease is accompanied by severe emotional and psychological burden. These drugs, which include methotrexate, cyclosporine, and acitretin (see eTable for recommended dosing), are advantageous in that they may be combined with other therapies; however, they have potential for dangerous toxicities.

Methotrexate is the most frequently utilized systemic therapy for psoriasis worldwide in children because of its low cost, once-weekly dosing, and the substantial amount of long-term efficacy and safety data available in the pediatric population. It is slow acting initially but has excellent long-term efficacy for nearly every subtype of psoriasis. The most common side effect of methotrexate is gastrointestinal tract intolerance. Nonetheless, adverse events are rare in children without prior history, with 1 large study (N=289) reporting no adverse events in more than 90% of patients aged 9 to 14 years treated with methotrexate.¹² Current guidelines recommend monitoring for bone marrow suppression and elevated transaminase levels 4 to 6 days after initiating treatment.¹ The absolute contraindications for methotrexate are pregnancy and liver disease, and caution should be taken in children with metabolic risk factors. Adolescents must be counseled regarding the elevated risk for hepatotoxicity associated with alcohol ingestion. Methotrexate therapy also requires 1 mg folic acid supplementation 6 to 7 days a week, which decreases the risk for developing folic acid deficiency and may decrease gastrointestinal tract intolerance and hepatic side effects that may result from therapy.

Cyclosporine is an effective and well-tolerated option for rapid control of severe psoriasis in children. It is useful for various types of psoriasis but generally is reserved for more severe subtypes, such as generalized pustular psoriasis, erythrodermic psoriasis, and uncontrolled plaque psoriasis. Long-term use of cyclosporine may result in renal toxicity and hypertension, and this therapy is absolutely contraindicated in children with kidney disease or hypertension at baseline. It is strongly recommended to evaluate blood pressure every week for the first month of therapy and at every subsequent follow-up visit, which may occur at variable intervals based on the judgement of the provider. Evaluation before and during treatment with cyclosporine also should include a complete blood cell count, complete metabolic panel, and lipid panel.

Systemic retinoids have a unique advantage over methotrexate and cyclosporine in that they are not immunosuppressive and therefore are not contraindicated in children who are very young or immunosuppressed. Children receiving systemic retinoids also can receive routine live vaccines—measles-mumps-rubella, varicella zoster, and rotavirus—that are contraindicated with other systemic therapies. Acitretin is particularly effective in pediatric patients with diffuse guttate psoriasis, pustular psoriasis, and palmoplantar psoriasis. Narrowband UVB therapy has been shown to augment the effectiveness of acitretin in children, which may allow for reduced acitretin dosing. Pustular psoriasis may respond as quickly as 3 weeks after initiation, whereas it may take 2 to 3 months before improvement is noticed in plaque psoriasis. Side effects of retinoids include skin dryness, hyperlipidemia, and gastrointestinal tract upset. The most severe long-term concern is skeletal toxicity, including premature epiphyseal closure, hyperostosis, periosteal bone formation, and decreased bone mineral density.¹ Vitamin A derivatives also are known teratogens and should be avoided in females of childbearing potential. Lipids and transaminases should be monitored routinely, and screening for depression and psychiatric symptoms should be performed frequently.¹

When utilizing systemic therapies, the objective should be to control the disease, maintain stability, and ultimately taper to the lowest effective dose or transition to a topical therapy, if feasible. Although no particular systemic therapy is recommended as first line for children with psoriasis, it is important to consider comorbidities, contraindications, monitoring frequency, mode of administration (injectable therapies elicit more psychological trauma in children than oral therapies), and expense when determining the best choice.

Biologics

Biologic agents are associated with very high to total psoriatic plaque clearance rates and require infrequent dosing and monitoring. However, their use may be limited by cost and injection phobias in children as well as limited evidence for their efficacy and safety in pediatric psoriasis. Several studies have established the safety and effectiveness of biologics in children with plaque psoriasis (see eTable for recommended dosing), whereas the evidence supporting their use in treating pustular and erythrodermic variants are limited to case reports and case series. The tumor necrosis factor α (TNF-α) inhibitor etanercept has been approved for use in children aged 4 years and older, and the IL-12/IL-23 inhibitor ustekinumab is approved in children aged 6 years and older. Other TNF-α inhibitors, namely infliximab and adalimumab, commonly are utilized off label for pediatric psoriasis. The most common side effect of biologic therapies in pediatric patients is injection-site reactions.¹ Prior to initiating therapy, children must undergo tuberculosis screening either by purified protein derivative testing or IFN-γ release assay. Testing should be repeated annually in individuals taking TNF-α inhibitors, though the utility of repeat testing when taking biologics in other classes is not clear. High-risk patients also should be screened for human immunodeficiency virus and hepatitis. Follow-up frequency may range from every 3 months to annually, based on judgement of the provider. In children who develop loss of response to biologics, methotrexate can be added to the regimen to attenuate formation of efficacy-reducing antidrug antibodies.

Final Thoughts

When managing children with psoriasis, it is important for dermatologists to appropriately educate guardians and children on the disease course, as well as consider the psychological, emotional, social, and financial factors that may direct decision-making regarding optimal therapeutics. Dermatologists should consider collaboration with the child’s primary care physician and other specialists to ensure that all needs are met.

These guidelines provide a framework agreed upon by numerous experts in pediatric psoriasis, but they are limited by gaps in the research. There still is much to be learned regarding the pathophysiology of psoriasis; the risk for developing comorbidities during adulthood; and the efficacy and safety of certain therapeutics, particularly biologics, in pediatric patients with psoriasis.

In November 2019, the American Academy of Dermatology (AAD) and the National Psoriasis Foundation (NPF) released their first set of recommendations for the management of pediatric psoriasis.¹ The pediatric guidelines discuss methods of quantifying disease severity in children, triggers and comorbidities, and the efficacy and safety of various therapeutic agents. This review aims to discuss, in a condensed form, special considerations unique to the management of children with psoriasis as presented in the guidelines as well as grade A– and grade B–level treatment recommendations (Table).

Quantifying Psoriasis Severity in Children

Percentage body surface area (BSA) involvement is the most common mode of grading psoriasis severity, with less than 3% BSA involvement being considered mild, 3% to 10% BSA moderate, and more than 10% severe disease. In children, the standard method of measuring BSA is the rule of 9’s: the head and each arm make up 9% of the total BSA, each leg and the front and back of the torso respectively each make up 18%, and the genitalia make up 1%. It also is important to consider impact on quality of life, which may be remarkable in spite of limited BSA involvement. The children’s dermatology life quality index score may be utilized in combination with affected BSA to determine the burden of psoriasis in context of impact on daily life. This metric is available in both written and cartoon form, and it consists of 10 questions that include variables such as severity of itch, impact on social life, and effects on sleep. Most notably, this tool incorporates pruritus,² which generally is addressed inadequately in pediatric psoriasis.

Triggers and Comorbidities in Pediatric Patients

In children, it is important to identify and eliminate modifiable factors that may prompt psoriasis flares. Infections, particularly group A beta-hemolytic streptococcal infections, are a major trigger in neonates and infants. Other exacerbating factors in children include emotional stress, secondhand cigarette smoke, Kawasaki disease, and withdrawal from systemic corticosteroids.

Psoriatic arthritis (PsA) is a burdensome comorbidity affecting children with psoriasis. The prevalence of joint disease is 15-times greater in children with psoriasis vs those without,³ and 80% of children with PsA develop rheumatologic symptoms, which typically include oligoarticular disease and dactylitis in infants and girls and enthesitis and axial joint involvement in boys and older children, years prior to the onset of cutaneous disease.⁴ Uveitis often occurs in children with psoriasis and PsA but not in those with isolated cutaneous disease.

Compared to unaffected children, pediatric patients with psoriasis have greater prevalence of metabolic and cardiovascular risk factors during childhood, including central obesity, hypertension, hypertriglyceridemia, hypercholesterolemia, insulin resistance, atherosclerosis, arrythmia, and valvular heart disease. Family history of obesity increases the risk for early-onset development of cutaneous lesions,^5,6 and weight reduction may alleviate severity of psoriasis lesions.⁷ In the United States, many of the metabolic associations observed are particularly robust in Black and Hispanic children vs those of other races. Furthermore, the prevalence of inflammatory bowel disease is 3- to 4-times higher in children with psoriasis compared to those without.

As with other cutaneous diseases, it is important to be aware of social and mental health concerns in children with psoriasis. The majority of pediatric patients with psoriasis experience name-calling, shaming, or bullying, and many have concerns from skin shedding and malodor. Independent risk for depression after the onset of psoriasis is high. Affected older children and adolescents are at increased risk for alcohol and drug abuse as well as eating disorders.

Despite these identified comorbidities, there are no unique screening recommendations for arthritis, ophthalmologic disease, metabolic disease, cardiovascular disease, gastrointestinal tract disease, or mental health issues in children with psoriasis. Rather, these patients should be monitored according to the American Academy of Pediatrics or American Diabetes Association guidelines for all pediatric patients.^8,9 Nonetheless, educating patients and guardians about these potential issues may be warranted.

Topical Therapies

For children with mild to moderate psoriasis, topical therapies are first line. Despite being off label, topical corticosteroids are the mainstay of therapy for localized psoriatic plaques in children. Topical vitamin D analogues—calcitriol and calcipotriol/calcipotriene—are highly effective and well tolerated, and they frequently are used in combination with topical corticosteroids. Topical calcineurin inhibitors, namely tacrolimus, also are used off label but are considered first line for sensitive regions of the skin in children, including the face, genitalia, and body folds. There currently is limited evidence for supporting the use of the topical vitamin A analogue tazarotene in children with psoriasis, though some consider its off-label use effective for pediatric nail psoriasis. It also may be used as an adjunct to topical corticosteroids to minimize irritation.

Although there is no gold standard topical regimen, combination therapy with a high-potency topical steroid and topical vitamin D analogue commonly is used to minimize steroid-induced side effects. For the first 2 weeks of treatment, they each may be applied once daily or mixed together and applied twice daily. For subsequent maintenance, topical calcipotriene may be applied on weekdays and topical steroids only on weekends. Combination calcipotriol–betamethasone dipropionate also is available as cream, ointment, foam, and suspension vehicles for use on the body and scalp in children aged 12 years and older. Tacrolimus ointment 0.1% may be applied in a thin layer up to twice daily. Concurrent emollient use also is recommended with these therapies.

Health care providers should educate patients and guardians about the potential side effects of topical therapies. They also should provide explicit instructions for amount, site, frequency, and duration of application. Topical corticosteroids commonly result in burning on application and may potentially cause skin thinning and striae with overuse. Topical vitamin D analogues may result in local irritation that may be improved by concurrent emollient use, and they generally should be avoided on sensitive sites. Topical calcineurin inhibitors are associated with burning, stinging, and pruritus, and the US Food and Drug Administration has issued a black-box warning related to risk for lymphoma with their chronic intermittent use. However, it was based on rare reports of lymphoma in transplant patients taking oral calcineurin inhibitors; no clinical trials to date in humans have demonstrated an increased risk for malignancy with topical calcineurin inhibitors.¹⁰ Tazarotene should be used cautiously in females of childbearing age given its teratogenic potential.

Children younger than 7 years are especially prone to suppression of the hypothalamic-pituitary-adrenal axis from topical corticosteroid therapy and theoretically hypercalcemia and hypervitaminosis D from topical vitamin D analogues, as their high BSA-to-volume ratio increases potential for systemic absorption. Children should avoid occlusive application of topical vitamin D analogues to large areas of the skin. Monitoring of vitamin D metabolites in the serum may be considered if calcipotriene or calcipotriol application to a large BSA is warranted.

Light-Based Therapy

In children with widespread psoriasis or those refractory to topical therapy, phototherapy may be considered. Narrowband UVB (311- to 313-nm wavelength) therapy is considered a first-line form of phototherapy in pediatric psoriasis. Mineral oil or emollient pretreatment to affected areas may augment the efficacy of UV-based treatments.¹¹ Excimer laser and UVA also may be efficacious, though evidence is limited in children. Treatment is recommended to start at 3 days a week, and once improvement is seen, the frequency can be decreased to 2 days a week. Once desired clearance is achieved, maintenance therapy can be continued at even longer intervals. Adjunctive use of tar preparations may potentiate the efficacy of phototherapy, though there is a theoretical increased risk for carcinogenicity with prolonged use of coal tar. Side effects of phototherapy include erythema, blistering hyperpigmentation, and pruritus. Psoralen is contraindicated in children younger than 12 years. All forms of phototherapy are contraindicated in children with generalized erythroderma and cutaneous cancer syndromes. Other important pediatric-specific considerations include anxiety that may be provoked by UV light machines and inconvenience of frequent appointments.

Nonbiologic Systemic Therapies

Systemic therapies may be considered in children with recalcitrant, widespread, or rapidly progressing psoriasis, particularly if the disease is accompanied by severe emotional and psychological burden. These drugs, which include methotrexate, cyclosporine, and acitretin (see eTable for recommended dosing), are advantageous in that they may be combined with other therapies; however, they have potential for dangerous toxicities.

Methotrexate is the most frequently utilized systemic therapy for psoriasis worldwide in children because of its low cost, once-weekly dosing, and the substantial amount of long-term efficacy and safety data available in the pediatric population. It is slow acting initially but has excellent long-term efficacy for nearly every subtype of psoriasis. The most common side effect of methotrexate is gastrointestinal tract intolerance. Nonetheless, adverse events are rare in children without prior history, with 1 large study (N=289) reporting no adverse events in more than 90% of patients aged 9 to 14 years treated with methotrexate.¹² Current guidelines recommend monitoring for bone marrow suppression and elevated transaminase levels 4 to 6 days after initiating treatment.¹ The absolute contraindications for methotrexate are pregnancy and liver disease, and caution should be taken in children with metabolic risk factors. Adolescents must be counseled regarding the elevated risk for hepatotoxicity associated with alcohol ingestion. Methotrexate therapy also requires 1 mg folic acid supplementation 6 to 7 days a week, which decreases the risk for developing folic acid deficiency and may decrease gastrointestinal tract intolerance and hepatic side effects that may result from therapy.

Cyclosporine is an effective and well-tolerated option for rapid control of severe psoriasis in children. It is useful for various types of psoriasis but generally is reserved for more severe subtypes, such as generalized pustular psoriasis, erythrodermic psoriasis, and uncontrolled plaque psoriasis. Long-term use of cyclosporine may result in renal toxicity and hypertension, and this therapy is absolutely contraindicated in children with kidney disease or hypertension at baseline. It is strongly recommended to evaluate blood pressure every week for the first month of therapy and at every subsequent follow-up visit, which may occur at variable intervals based on the judgement of the provider. Evaluation before and during treatment with cyclosporine also should include a complete blood cell count, complete metabolic panel, and lipid panel.

Systemic retinoids have a unique advantage over methotrexate and cyclosporine in that they are not immunosuppressive and therefore are not contraindicated in children who are very young or immunosuppressed. Children receiving systemic retinoids also can receive routine live vaccines—measles-mumps-rubella, varicella zoster, and rotavirus—that are contraindicated with other systemic therapies. Acitretin is particularly effective in pediatric patients with diffuse guttate psoriasis, pustular psoriasis, and palmoplantar psoriasis. Narrowband UVB therapy has been shown to augment the effectiveness of acitretin in children, which may allow for reduced acitretin dosing. Pustular psoriasis may respond as quickly as 3 weeks after initiation, whereas it may take 2 to 3 months before improvement is noticed in plaque psoriasis. Side effects of retinoids include skin dryness, hyperlipidemia, and gastrointestinal tract upset. The most severe long-term concern is skeletal toxicity, including premature epiphyseal closure, hyperostosis, periosteal bone formation, and decreased bone mineral density.¹ Vitamin A derivatives also are known teratogens and should be avoided in females of childbearing potential. Lipids and transaminases should be monitored routinely, and screening for depression and psychiatric symptoms should be performed frequently.¹

When utilizing systemic therapies, the objective should be to control the disease, maintain stability, and ultimately taper to the lowest effective dose or transition to a topical therapy, if feasible. Although no particular systemic therapy is recommended as first line for children with psoriasis, it is important to consider comorbidities, contraindications, monitoring frequency, mode of administration (injectable therapies elicit more psychological trauma in children than oral therapies), and expense when determining the best choice.

Biologics

Biologic agents are associated with very high to total psoriatic plaque clearance rates and require infrequent dosing and monitoring. However, their use may be limited by cost and injection phobias in children as well as limited evidence for their efficacy and safety in pediatric psoriasis. Several studies have established the safety and effectiveness of biologics in children with plaque psoriasis (see eTable for recommended dosing), whereas the evidence supporting their use in treating pustular and erythrodermic variants are limited to case reports and case series. The tumor necrosis factor α (TNF-α) inhibitor etanercept has been approved for use in children aged 4 years and older, and the IL-12/IL-23 inhibitor ustekinumab is approved in children aged 6 years and older. Other TNF-α inhibitors, namely infliximab and adalimumab, commonly are utilized off label for pediatric psoriasis. The most common side effect of biologic therapies in pediatric patients is injection-site reactions.¹ Prior to initiating therapy, children must undergo tuberculosis screening either by purified protein derivative testing or IFN-γ release assay. Testing should be repeated annually in individuals taking TNF-α inhibitors, though the utility of repeat testing when taking biologics in other classes is not clear. High-risk patients also should be screened for human immunodeficiency virus and hepatitis. Follow-up frequency may range from every 3 months to annually, based on judgement of the provider. In children who develop loss of response to biologics, methotrexate can be added to the regimen to attenuate formation of efficacy-reducing antidrug antibodies.

Final Thoughts

When managing children with psoriasis, it is important for dermatologists to appropriately educate guardians and children on the disease course, as well as consider the psychological, emotional, social, and financial factors that may direct decision-making regarding optimal therapeutics. Dermatologists should consider collaboration with the child’s primary care physician and other specialists to ensure that all needs are met.

These guidelines provide a framework agreed upon by numerous experts in pediatric psoriasis, but they are limited by gaps in the research. There still is much to be learned regarding the pathophysiology of psoriasis; the risk for developing comorbidities during adulthood; and the efficacy and safety of certain therapeutics, particularly biologics, in pediatric patients with psoriasis.

In November 2019, the American Academy of Dermatology (AAD) and the National Psoriasis Foundation (NPF) released their first set of recommendations for the management of pediatric psoriasis.¹ The pediatric guidelines discuss methods of quantifying disease severity in children, triggers and comorbidities, and the efficacy and safety of various therapeutic agents. This review aims to discuss, in a condensed form, special considerations unique to the management of children with psoriasis as presented in the guidelines as well as grade A– and grade B–level treatment recommendations (Table).

Quantifying Psoriasis Severity in Children

Percentage body surface area (BSA) involvement is the most common mode of grading psoriasis severity, with less than 3% BSA involvement being considered mild, 3% to 10% BSA moderate, and more than 10% severe disease. In children, the standard method of measuring BSA is the rule of 9’s: the head and each arm make up 9% of the total BSA, each leg and the front and back of the torso respectively each make up 18%, and the genitalia make up 1%. It also is important to consider impact on quality of life, which may be remarkable in spite of limited BSA involvement. The children’s dermatology life quality index score may be utilized in combination with affected BSA to determine the burden of psoriasis in context of impact on daily life. This metric is available in both written and cartoon form, and it consists of 10 questions that include variables such as severity of itch, impact on social life, and effects on sleep. Most notably, this tool incorporates pruritus,² which generally is addressed inadequately in pediatric psoriasis.

Triggers and Comorbidities in Pediatric Patients

In children, it is important to identify and eliminate modifiable factors that may prompt psoriasis flares. Infections, particularly group A beta-hemolytic streptococcal infections, are a major trigger in neonates and infants. Other exacerbating factors in children include emotional stress, secondhand cigarette smoke, Kawasaki disease, and withdrawal from systemic corticosteroids.

Psoriatic arthritis (PsA) is a burdensome comorbidity affecting children with psoriasis. The prevalence of joint disease is 15-times greater in children with psoriasis vs those without,³ and 80% of children with PsA develop rheumatologic symptoms, which typically include oligoarticular disease and dactylitis in infants and girls and enthesitis and axial joint involvement in boys and older children, years prior to the onset of cutaneous disease.⁴ Uveitis often occurs in children with psoriasis and PsA but not in those with isolated cutaneous disease.

Compared to unaffected children, pediatric patients with psoriasis have greater prevalence of metabolic and cardiovascular risk factors during childhood, including central obesity, hypertension, hypertriglyceridemia, hypercholesterolemia, insulin resistance, atherosclerosis, arrythmia, and valvular heart disease. Family history of obesity increases the risk for early-onset development of cutaneous lesions,^5,6 and weight reduction may alleviate severity of psoriasis lesions.⁷ In the United States, many of the metabolic associations observed are particularly robust in Black and Hispanic children vs those of other races. Furthermore, the prevalence of inflammatory bowel disease is 3- to 4-times higher in children with psoriasis compared to those without.

As with other cutaneous diseases, it is important to be aware of social and mental health concerns in children with psoriasis. The majority of pediatric patients with psoriasis experience name-calling, shaming, or bullying, and many have concerns from skin shedding and malodor. Independent risk for depression after the onset of psoriasis is high. Affected older children and adolescents are at increased risk for alcohol and drug abuse as well as eating disorders.

Despite these identified comorbidities, there are no unique screening recommendations for arthritis, ophthalmologic disease, metabolic disease, cardiovascular disease, gastrointestinal tract disease, or mental health issues in children with psoriasis. Rather, these patients should be monitored according to the American Academy of Pediatrics or American Diabetes Association guidelines for all pediatric patients.^8,9 Nonetheless, educating patients and guardians about these potential issues may be warranted.

Topical Therapies

For children with mild to moderate psoriasis, topical therapies are first line. Despite being off label, topical corticosteroids are the mainstay of therapy for localized psoriatic plaques in children. Topical vitamin D analogues—calcitriol and calcipotriol/calcipotriene—are highly effective and well tolerated, and they frequently are used in combination with topical corticosteroids. Topical calcineurin inhibitors, namely tacrolimus, also are used off label but are considered first line for sensitive regions of the skin in children, including the face, genitalia, and body folds. There currently is limited evidence for supporting the use of the topical vitamin A analogue tazarotene in children with psoriasis, though some consider its off-label use effective for pediatric nail psoriasis. It also may be used as an adjunct to topical corticosteroids to minimize irritation.

Although there is no gold standard topical regimen, combination therapy with a high-potency topical steroid and topical vitamin D analogue commonly is used to minimize steroid-induced side effects. For the first 2 weeks of treatment, they each may be applied once daily or mixed together and applied twice daily. For subsequent maintenance, topical calcipotriene may be applied on weekdays and topical steroids only on weekends. Combination calcipotriol–betamethasone dipropionate also is available as cream, ointment, foam, and suspension vehicles for use on the body and scalp in children aged 12 years and older. Tacrolimus ointment 0.1% may be applied in a thin layer up to twice daily. Concurrent emollient use also is recommended with these therapies.

Health care providers should educate patients and guardians about the potential side effects of topical therapies. They also should provide explicit instructions for amount, site, frequency, and duration of application. Topical corticosteroids commonly result in burning on application and may potentially cause skin thinning and striae with overuse. Topical vitamin D analogues may result in local irritation that may be improved by concurrent emollient use, and they generally should be avoided on sensitive sites. Topical calcineurin inhibitors are associated with burning, stinging, and pruritus, and the US Food and Drug Administration has issued a black-box warning related to risk for lymphoma with their chronic intermittent use. However, it was based on rare reports of lymphoma in transplant patients taking oral calcineurin inhibitors; no clinical trials to date in humans have demonstrated an increased risk for malignancy with topical calcineurin inhibitors.¹⁰ Tazarotene should be used cautiously in females of childbearing age given its teratogenic potential.

Children younger than 7 years are especially prone to suppression of the hypothalamic-pituitary-adrenal axis from topical corticosteroid therapy and theoretically hypercalcemia and hypervitaminosis D from topical vitamin D analogues, as their high BSA-to-volume ratio increases potential for systemic absorption. Children should avoid occlusive application of topical vitamin D analogues to large areas of the skin. Monitoring of vitamin D metabolites in the serum may be considered if calcipotriene or calcipotriol application to a large BSA is warranted.

Light-Based Therapy

In children with widespread psoriasis or those refractory to topical therapy, phototherapy may be considered. Narrowband UVB (311- to 313-nm wavelength) therapy is considered a first-line form of phototherapy in pediatric psoriasis. Mineral oil or emollient pretreatment to affected areas may augment the efficacy of UV-based treatments.¹¹ Excimer laser and UVA also may be efficacious, though evidence is limited in children. Treatment is recommended to start at 3 days a week, and once improvement is seen, the frequency can be decreased to 2 days a week. Once desired clearance is achieved, maintenance therapy can be continued at even longer intervals. Adjunctive use of tar preparations may potentiate the efficacy of phototherapy, though there is a theoretical increased risk for carcinogenicity with prolonged use of coal tar. Side effects of phototherapy include erythema, blistering hyperpigmentation, and pruritus. Psoralen is contraindicated in children younger than 12 years. All forms of phototherapy are contraindicated in children with generalized erythroderma and cutaneous cancer syndromes. Other important pediatric-specific considerations include anxiety that may be provoked by UV light machines and inconvenience of frequent appointments.

Nonbiologic Systemic Therapies

Systemic therapies may be considered in children with recalcitrant, widespread, or rapidly progressing psoriasis, particularly if the disease is accompanied by severe emotional and psychological burden. These drugs, which include methotrexate, cyclosporine, and acitretin (see eTable for recommended dosing), are advantageous in that they may be combined with other therapies; however, they have potential for dangerous toxicities.

Methotrexate is the most frequently utilized systemic therapy for psoriasis worldwide in children because of its low cost, once-weekly dosing, and the substantial amount of long-term efficacy and safety data available in the pediatric population. It is slow acting initially but has excellent long-term efficacy for nearly every subtype of psoriasis. The most common side effect of methotrexate is gastrointestinal tract intolerance. Nonetheless, adverse events are rare in children without prior history, with 1 large study (N=289) reporting no adverse events in more than 90% of patients aged 9 to 14 years treated with methotrexate.¹² Current guidelines recommend monitoring for bone marrow suppression and elevated transaminase levels 4 to 6 days after initiating treatment.¹ The absolute contraindications for methotrexate are pregnancy and liver disease, and caution should be taken in children with metabolic risk factors. Adolescents must be counseled regarding the elevated risk for hepatotoxicity associated with alcohol ingestion. Methotrexate therapy also requires 1 mg folic acid supplementation 6 to 7 days a week, which decreases the risk for developing folic acid deficiency and may decrease gastrointestinal tract intolerance and hepatic side effects that may result from therapy.

Cyclosporine is an effective and well-tolerated option for rapid control of severe psoriasis in children. It is useful for various types of psoriasis but generally is reserved for more severe subtypes, such as generalized pustular psoriasis, erythrodermic psoriasis, and uncontrolled plaque psoriasis. Long-term use of cyclosporine may result in renal toxicity and hypertension, and this therapy is absolutely contraindicated in children with kidney disease or hypertension at baseline. It is strongly recommended to evaluate blood pressure every week for the first month of therapy and at every subsequent follow-up visit, which may occur at variable intervals based on the judgement of the provider. Evaluation before and during treatment with cyclosporine also should include a complete blood cell count, complete metabolic panel, and lipid panel.

Systemic retinoids have a unique advantage over methotrexate and cyclosporine in that they are not immunosuppressive and therefore are not contraindicated in children who are very young or immunosuppressed. Children receiving systemic retinoids also can receive routine live vaccines—measles-mumps-rubella, varicella zoster, and rotavirus—that are contraindicated with other systemic therapies. Acitretin is particularly effective in pediatric patients with diffuse guttate psoriasis, pustular psoriasis, and palmoplantar psoriasis. Narrowband UVB therapy has been shown to augment the effectiveness of acitretin in children, which may allow for reduced acitretin dosing. Pustular psoriasis may respond as quickly as 3 weeks after initiation, whereas it may take 2 to 3 months before improvement is noticed in plaque psoriasis. Side effects of retinoids include skin dryness, hyperlipidemia, and gastrointestinal tract upset. The most severe long-term concern is skeletal toxicity, including premature epiphyseal closure, hyperostosis, periosteal bone formation, and decreased bone mineral density.¹ Vitamin A derivatives also are known teratogens and should be avoided in females of childbearing potential. Lipids and transaminases should be monitored routinely, and screening for depression and psychiatric symptoms should be performed frequently.¹

When utilizing systemic therapies, the objective should be to control the disease, maintain stability, and ultimately taper to the lowest effective dose or transition to a topical therapy, if feasible. Although no particular systemic therapy is recommended as first line for children with psoriasis, it is important to consider comorbidities, contraindications, monitoring frequency, mode of administration (injectable therapies elicit more psychological trauma in children than oral therapies), and expense when determining the best choice.

Biologics

Biologic agents are associated with very high to total psoriatic plaque clearance rates and require infrequent dosing and monitoring. However, their use may be limited by cost and injection phobias in children as well as limited evidence for their efficacy and safety in pediatric psoriasis. Several studies have established the safety and effectiveness of biologics in children with plaque psoriasis (see eTable for recommended dosing), whereas the evidence supporting their use in treating pustular and erythrodermic variants are limited to case reports and case series. The tumor necrosis factor α (TNF-α) inhibitor etanercept has been approved for use in children aged 4 years and older, and the IL-12/IL-23 inhibitor ustekinumab is approved in children aged 6 years and older. Other TNF-α inhibitors, namely infliximab and adalimumab, commonly are utilized off label for pediatric psoriasis. The most common side effect of biologic therapies in pediatric patients is injection-site reactions.¹ Prior to initiating therapy, children must undergo tuberculosis screening either by purified protein derivative testing or IFN-γ release assay. Testing should be repeated annually in individuals taking TNF-α inhibitors, though the utility of repeat testing when taking biologics in other classes is not clear. High-risk patients also should be screened for human immunodeficiency virus and hepatitis. Follow-up frequency may range from every 3 months to annually, based on judgement of the provider. In children who develop loss of response to biologics, methotrexate can be added to the regimen to attenuate formation of efficacy-reducing antidrug antibodies.

Final Thoughts

When managing children with psoriasis, it is important for dermatologists to appropriately educate guardians and children on the disease course, as well as consider the psychological, emotional, social, and financial factors that may direct decision-making regarding optimal therapeutics. Dermatologists should consider collaboration with the child’s primary care physician and other specialists to ensure that all needs are met.

These guidelines provide a framework agreed upon by numerous experts in pediatric psoriasis, but they are limited by gaps in the research. There still is much to be learned regarding the pathophysiology of psoriasis; the risk for developing comorbidities during adulthood; and the efficacy and safety of certain therapeutics, particularly biologics, in pediatric patients with psoriasis.