Jennifer G. Powers, MD

A patient presenting with a hand pustule is a phenomenon encountered worldwide requiring careful history-taking. Some occupations, activities, and various religious practices (eg, Eid al-Adha, Passover, Easter) have been implicated worldwide in orf infection. In the United States, orf virus usually is spread from infected animal hosts to humans. Herein, we review the differential for a single hand pustule, which includes both infectious and noninfectious causes. Recognizing orf virus as the etiology of a cutaneous hand pustule in patients is important, as misdiagnosis can lead to unnecessary invasive testing and/or treatments with suboptimal clinical outcomes.

Case Series

When conducting a search for orf virus cases at our institution (University of Iowa Hospitals and Clinics, Iowa City, Iowa), 5 patient cases were identified.

Patient 1—A 27-year-old otherwise healthy woman presented to clinic with a tender red bump on the right ring finger that had been slowly growing over the course of 2 weeks and had recently started to bleed. A social history revealed that she owned several goats, which she frequently milked; 1 of the goats had a cyst on the mouth, which she popped approximately 1 to 2 weeks prior to the appearance of the lesion on the finger. She also endorsed that she owned several cattle and various other animals with which she had frequent contact. A biopsy was obtained with features consistent with orf virus.

Patient 2—A 33-year-old man presented to clinic with a lesion of concern on the left index finger. Several days prior to presentation, the patient had visited the emergency department for swelling and erythema of the same finger after cutting himself with a knife while preparing sheep meat. Radiographs were normal, and the patient was referred to dermatology. In clinic, there was a 0.5-cm fluctuant mass on the distal interphalangeal joint of the third finger. The patient declined a biopsy, and the lesion healed over 4 to 6 weeks without complication.

Patient 3—A 38-year-old man presented to clinic with 2 painless, large, round nodules on the right proximal index finger, with open friable centers noted on physical examination (Figure 1). The patient reported cutting the finger while preparing sheep meat several days prior. The nodules had been present for a few weeks and continued to grow. A punch biopsy revealed evidence of parapoxvirus infection consistent with a diagnosis of orf.

Patient 4—A 48-year-old man was referred to our dermatology clinic for evaluation of a bleeding lesion on the left middle finger. Physical examination revealed an exophytic, friable, ulcerated nodule on the dorsal aspect of the left middle finger (Figure 2). Upon further questioning, the patient mentioned that he handled raw lamb meat after cutting the finger. A punch biopsy was obtained and was consistent with orf virus infection.

Patient 5—A 43-year-old woman presented to clinic with a chronic wound on the mid lower back that was noted to drain and crust over. She thought the lesion was improving, but it had become painful over the last few weeks. A shave biopsy of the lesion was consistent with orf virus. At follow-up, the patient was unable to identify any recent contact with animals.

Transmission From Animals to Humans—Orf virus is a member of the Parapoxvirus genus of the Poxviridae family.¹ This virus is highly contagious among animals and has been described around the globe. The resulting disease also is known as contagious pustular dermatitis,² soremuzzle,³ ecthyma contagiosum of sheep,⁴ and scabby mouth.⁵ This virus most commonly infects young lambs and manifests as raw to crusty papules, pustules, or vesicles around the mouth and nose of the animal.⁴ Additional signs include excessive salivation and weight loss or starvation from the inability to suckle because of the lesions.⁵ Although ecthyma contagiosum infection of sheep and goats has been well known for centuries, human infection was first reported in the literature in 1934.⁶

Transmission of orf to humans can occur when direct contact with an infected animal exhibiting active lesions occurs.⁷ Orf virus also can be transmitted through fomites (eg, from knives, wool, buildings, equipment) that previously were in contact with infected animals, making it relevant to ask all farmers about any animals with pustules around the mouth, nose, udders, or other commonly affected areas. Although sanitation efforts are important for prevention, orf virus is hardy, and fomites can remain on surfaces for many months.⁸ Transmission among animals and from animals to humans frequently occurs; however, human-to-human transmission is less common.⁹ Ecthyma contagiosum is considered an occupational hazard, with the disease being most prevalent in shepherds, veterinarians, and butchers.^1,8 Disease prevalence in these occupations has been reported to be as high as 50%.¹⁰ Infections also are seen in patients who attend petting zoos or who slaughter goats and sheep for cultural practices.⁸

Clinical Characteristics in Humans—The clinical diagnosis of orf is dependent on taking a thorough patient history that includes social, occupational, and religious activities. Development of a nodule or papule on a patient’s hand with recent exposure to fomites or direct contact with a goat or sheep up to 1 week prior is extremely suggestive of an orf virus infection.

Clinically, orf most often begins as an individual papule or nodule on the dorsal surface of the patient’s finger or hand and ranges from completely asymptomatic to pruritic or even painful.^1,8 Depending on how the infection was inoculated, lesions can vary in size and number. Other sites that have been reported less frequently include the genitals, legs, axillae, and head.^11,12 Lesions are roughly 1 cm in diameter but can vary in size. Ecthyma contagiosum is not a static disease but changes in appearance over the course of infection. Typically, lesions will appear 3 to 7 days after inoculation with the orf virus and will self-resolve 6 to 8 weeks later.

Orf lesions have been described to progress through 6 distinct phases before resolving: maculopapular (erythematous macule or papule forms), targetoid (formation of a necrotic center with red outer halo), acute (lesion begins to weep), regenerative (lesion becomes dry), papilloma (dry crust becomes papillomatous), and regression (skin returns to normal appearance).^1,8,9 Each phase of ecthyma contagiosum is unique and will last up to 1 week before progressing. Because of this prolonged clinical course, patients can present at any stage.

Reports of systemic symptoms are uncommon but can include lymphadenopathy, fever, and malaise.¹³ Although the disease course in immunocompetent individuals is quite mild, immunocompromised patients may experience persistent orf lesions that are painful and can be much larger, with reports of several centimeters in diameter.¹⁴

Dermatopathology and Molecular Studies—When a clinical diagnosis is not possible, biopsy or molecular studies can be helpful.⁸ Histopathology can vary depending on the phase of the lesion. Early stages are characterized by spongiform degeneration of the epidermis with variable vesiculation of the superficial epidermis and eosinophilic cytoplasmic inclusion bodies of keratinocytes (Figure 3). Later stages demonstrate full-thickness necrosis with epidermal balloon degeneration and dense inflammation of the dermis with edema and extravasated erythrocytes from dilated blood vessels. Both early- and late-stage disease commonly show characteristic elongated thin rete ridges.⁸

Molecular studies are another reliable method for diagnosis, though these are not always readily available. Polymerase chain reaction can be used for sensitive and rapid diagnosis.¹⁵ Less commonly, electron microscopy, Western blot, or enzyme-linked immunosorbent assays are used.¹⁶ Laboratory studies, such as complete blood cell count with differential, erythrocyte sedimentation rate, and C-reactive protein, often are unnecessary but may be helpful in ruling out other infectious causes. Tissue culture can be considered if bacterial, fungal, or acid-fast bacilli are in the differential; however, no growth will be seen in the case of orf viral infection.

Differential Diagnosis—The differential diagnosis for patients presenting with a large pustule on the hand or fingers can depend on geographic location, as the potential etiology may vary widely around the world. Several zoonotic viral infections other than orf can present with pustular lesions on the hands (Table).^17-24

Clinically, infection with these named viruses can be hard to distinguish; however, appropriate social history or polymerase chain reaction can be obtained to differentiate them. Other infectious entities include herpetic whitlow, giant molluscum, and anthrax (eTable).^24-26 Biopsy of the lesion with bacterial tissue culture may lead to definitive diagnosis.²⁶

Treatment—Because of the self-resolving nature of orf, treatment usually is not needed in immunocompetent patients with a solitary lesion. However, wound care is essential to prevent secondary infections of the lesion. If secondarily infected, topical or oral antibiotics may be prescribed. Immunocompromised individuals are at increased risk for developing large persistent lesions and sometimes require intervention for successful treatment. Several successful treatment methods have been described and include intralesional interferon injections, electrocautery, topical imiquimod, topical cidofovir, and cryotherapy.^8,14,27-30 Infections that continue to be refractory to less-invasive treatment can be considered for wide local excision; however, recurrence is possible.⁸ Vaccinations are available for animals to prevent the spread of infection in the flock, but there are no formulations of vaccines for human use. Prevention of spread to humans can be done through animal vaccination, careful handling of animal products while wearing nonporous gloves, and proper sanitation techniques.

Complications—Orf has an excellent long-term prognosis in immunocompetent patients, as the virus is epitheliotropic, and inoculation does not lead to viremia.² Although lesions typically are asymptomatic in most patients, complications can occur, especially in immunosuppressed individuals. These complications include systemic symptoms, giant persistent lesions prone to infection or scarring, erysipelas, lymphadenitis, and erythema multiforme.^8,31 Common systemic symptoms of ecthyma contagiosum include fever, fatigue, and myalgia. Lymphadenitis can occur along with local swelling and lymphatic streaking. Although erythema multiforme is a rare complication occurring after initial ecthyma contagiosum infection, this hypersensitivity reaction is postulated to be in response to the immunologic clearing of the orf virus.^32,33 Patients receiving systemic immunosuppressive medications are at an increased risk of developing complications from infection and may even be required to pause systemic treatment for complete resolution of orf lesions.³⁴ Other cutaneous diseases that decrease the skin’s barrier protection, such as bullous pemphigoid or eczema, also can place patients at an increased risk for complications.³⁵ Although human-to-human orf virus transmission is exceptionally rare, there is a case report of this phenomenon in immunosuppressed patients residing in a burn unit.³⁶ Transplant recipients on immunosuppressive medications also can experience orf lesions with exaggerated presentations that continue to grow up to several centimeters in diameter.³¹ Long-term prognosis is still good in these patients with appropriate disease recognition and treatment. Reinfection is not uncommon with repeated exposure to the source, but lesions are less severe and resolve faster than with initial infection.^1,8

Conclusion

The contagious hand pustule caused by orf virus is a distinct clinical entity that is prevalent worldwide and requires thorough evaluation of the clinical course of the lesion and the patient’s social history. Several zoonotic viral infections have been implicated in this presentation. Although biopsy and molecular studies can be helpful, the expert diagnostician can make a clinical diagnosis with careful attention to social history, geographic location, and cultural practices.

A patient presenting with a hand pustule is a phenomenon encountered worldwide requiring careful history-taking. Some occupations, activities, and various religious practices (eg, Eid al-Adha, Passover, Easter) have been implicated worldwide in orf infection. In the United States, orf virus usually is spread from infected animal hosts to humans. Herein, we review the differential for a single hand pustule, which includes both infectious and noninfectious causes. Recognizing orf virus as the etiology of a cutaneous hand pustule in patients is important, as misdiagnosis can lead to unnecessary invasive testing and/or treatments with suboptimal clinical outcomes.

Case Series

When conducting a search for orf virus cases at our institution (University of Iowa Hospitals and Clinics, Iowa City, Iowa), 5 patient cases were identified.

Patient 1—A 27-year-old otherwise healthy woman presented to clinic with a tender red bump on the right ring finger that had been slowly growing over the course of 2 weeks and had recently started to bleed. A social history revealed that she owned several goats, which she frequently milked; 1 of the goats had a cyst on the mouth, which she popped approximately 1 to 2 weeks prior to the appearance of the lesion on the finger. She also endorsed that she owned several cattle and various other animals with which she had frequent contact. A biopsy was obtained with features consistent with orf virus.

Patient 2—A 33-year-old man presented to clinic with a lesion of concern on the left index finger. Several days prior to presentation, the patient had visited the emergency department for swelling and erythema of the same finger after cutting himself with a knife while preparing sheep meat. Radiographs were normal, and the patient was referred to dermatology. In clinic, there was a 0.5-cm fluctuant mass on the distal interphalangeal joint of the third finger. The patient declined a biopsy, and the lesion healed over 4 to 6 weeks without complication.

Patient 3—A 38-year-old man presented to clinic with 2 painless, large, round nodules on the right proximal index finger, with open friable centers noted on physical examination (Figure 1). The patient reported cutting the finger while preparing sheep meat several days prior. The nodules had been present for a few weeks and continued to grow. A punch biopsy revealed evidence of parapoxvirus infection consistent with a diagnosis of orf.

Patient 4—A 48-year-old man was referred to our dermatology clinic for evaluation of a bleeding lesion on the left middle finger. Physical examination revealed an exophytic, friable, ulcerated nodule on the dorsal aspect of the left middle finger (Figure 2). Upon further questioning, the patient mentioned that he handled raw lamb meat after cutting the finger. A punch biopsy was obtained and was consistent with orf virus infection.

Patient 5—A 43-year-old woman presented to clinic with a chronic wound on the mid lower back that was noted to drain and crust over. She thought the lesion was improving, but it had become painful over the last few weeks. A shave biopsy of the lesion was consistent with orf virus. At follow-up, the patient was unable to identify any recent contact with animals.

Transmission From Animals to Humans—Orf virus is a member of the Parapoxvirus genus of the Poxviridae family.¹ This virus is highly contagious among animals and has been described around the globe. The resulting disease also is known as contagious pustular dermatitis,² soremuzzle,³ ecthyma contagiosum of sheep,⁴ and scabby mouth.⁵ This virus most commonly infects young lambs and manifests as raw to crusty papules, pustules, or vesicles around the mouth and nose of the animal.⁴ Additional signs include excessive salivation and weight loss or starvation from the inability to suckle because of the lesions.⁵ Although ecthyma contagiosum infection of sheep and goats has been well known for centuries, human infection was first reported in the literature in 1934.⁶

Transmission of orf to humans can occur when direct contact with an infected animal exhibiting active lesions occurs.⁷ Orf virus also can be transmitted through fomites (eg, from knives, wool, buildings, equipment) that previously were in contact with infected animals, making it relevant to ask all farmers about any animals with pustules around the mouth, nose, udders, or other commonly affected areas. Although sanitation efforts are important for prevention, orf virus is hardy, and fomites can remain on surfaces for many months.⁸ Transmission among animals and from animals to humans frequently occurs; however, human-to-human transmission is less common.⁹ Ecthyma contagiosum is considered an occupational hazard, with the disease being most prevalent in shepherds, veterinarians, and butchers.^1,8 Disease prevalence in these occupations has been reported to be as high as 50%.¹⁰ Infections also are seen in patients who attend petting zoos or who slaughter goats and sheep for cultural practices.⁸

Clinical Characteristics in Humans—The clinical diagnosis of orf is dependent on taking a thorough patient history that includes social, occupational, and religious activities. Development of a nodule or papule on a patient’s hand with recent exposure to fomites or direct contact with a goat or sheep up to 1 week prior is extremely suggestive of an orf virus infection.

Clinically, orf most often begins as an individual papule or nodule on the dorsal surface of the patient’s finger or hand and ranges from completely asymptomatic to pruritic or even painful.^1,8 Depending on how the infection was inoculated, lesions can vary in size and number. Other sites that have been reported less frequently include the genitals, legs, axillae, and head.^11,12 Lesions are roughly 1 cm in diameter but can vary in size. Ecthyma contagiosum is not a static disease but changes in appearance over the course of infection. Typically, lesions will appear 3 to 7 days after inoculation with the orf virus and will self-resolve 6 to 8 weeks later.

Orf lesions have been described to progress through 6 distinct phases before resolving: maculopapular (erythematous macule or papule forms), targetoid (formation of a necrotic center with red outer halo), acute (lesion begins to weep), regenerative (lesion becomes dry), papilloma (dry crust becomes papillomatous), and regression (skin returns to normal appearance).^1,8,9 Each phase of ecthyma contagiosum is unique and will last up to 1 week before progressing. Because of this prolonged clinical course, patients can present at any stage.

Reports of systemic symptoms are uncommon but can include lymphadenopathy, fever, and malaise.¹³ Although the disease course in immunocompetent individuals is quite mild, immunocompromised patients may experience persistent orf lesions that are painful and can be much larger, with reports of several centimeters in diameter.¹⁴

Dermatopathology and Molecular Studies—When a clinical diagnosis is not possible, biopsy or molecular studies can be helpful.⁸ Histopathology can vary depending on the phase of the lesion. Early stages are characterized by spongiform degeneration of the epidermis with variable vesiculation of the superficial epidermis and eosinophilic cytoplasmic inclusion bodies of keratinocytes (Figure 3). Later stages demonstrate full-thickness necrosis with epidermal balloon degeneration and dense inflammation of the dermis with edema and extravasated erythrocytes from dilated blood vessels. Both early- and late-stage disease commonly show characteristic elongated thin rete ridges.⁸

Molecular studies are another reliable method for diagnosis, though these are not always readily available. Polymerase chain reaction can be used for sensitive and rapid diagnosis.¹⁵ Less commonly, electron microscopy, Western blot, or enzyme-linked immunosorbent assays are used.¹⁶ Laboratory studies, such as complete blood cell count with differential, erythrocyte sedimentation rate, and C-reactive protein, often are unnecessary but may be helpful in ruling out other infectious causes. Tissue culture can be considered if bacterial, fungal, or acid-fast bacilli are in the differential; however, no growth will be seen in the case of orf viral infection.

Differential Diagnosis—The differential diagnosis for patients presenting with a large pustule on the hand or fingers can depend on geographic location, as the potential etiology may vary widely around the world. Several zoonotic viral infections other than orf can present with pustular lesions on the hands (Table).^17-24

Clinically, infection with these named viruses can be hard to distinguish; however, appropriate social history or polymerase chain reaction can be obtained to differentiate them. Other infectious entities include herpetic whitlow, giant molluscum, and anthrax (eTable).^24-26 Biopsy of the lesion with bacterial tissue culture may lead to definitive diagnosis.²⁶

Treatment—Because of the self-resolving nature of orf, treatment usually is not needed in immunocompetent patients with a solitary lesion. However, wound care is essential to prevent secondary infections of the lesion. If secondarily infected, topical or oral antibiotics may be prescribed. Immunocompromised individuals are at increased risk for developing large persistent lesions and sometimes require intervention for successful treatment. Several successful treatment methods have been described and include intralesional interferon injections, electrocautery, topical imiquimod, topical cidofovir, and cryotherapy.^8,14,27-30 Infections that continue to be refractory to less-invasive treatment can be considered for wide local excision; however, recurrence is possible.⁸ Vaccinations are available for animals to prevent the spread of infection in the flock, but there are no formulations of vaccines for human use. Prevention of spread to humans can be done through animal vaccination, careful handling of animal products while wearing nonporous gloves, and proper sanitation techniques.

Complications—Orf has an excellent long-term prognosis in immunocompetent patients, as the virus is epitheliotropic, and inoculation does not lead to viremia.² Although lesions typically are asymptomatic in most patients, complications can occur, especially in immunosuppressed individuals. These complications include systemic symptoms, giant persistent lesions prone to infection or scarring, erysipelas, lymphadenitis, and erythema multiforme.^8,31 Common systemic symptoms of ecthyma contagiosum include fever, fatigue, and myalgia. Lymphadenitis can occur along with local swelling and lymphatic streaking. Although erythema multiforme is a rare complication occurring after initial ecthyma contagiosum infection, this hypersensitivity reaction is postulated to be in response to the immunologic clearing of the orf virus.^32,33 Patients receiving systemic immunosuppressive medications are at an increased risk of developing complications from infection and may even be required to pause systemic treatment for complete resolution of orf lesions.³⁴ Other cutaneous diseases that decrease the skin’s barrier protection, such as bullous pemphigoid or eczema, also can place patients at an increased risk for complications.³⁵ Although human-to-human orf virus transmission is exceptionally rare, there is a case report of this phenomenon in immunosuppressed patients residing in a burn unit.³⁶ Transplant recipients on immunosuppressive medications also can experience orf lesions with exaggerated presentations that continue to grow up to several centimeters in diameter.³¹ Long-term prognosis is still good in these patients with appropriate disease recognition and treatment. Reinfection is not uncommon with repeated exposure to the source, but lesions are less severe and resolve faster than with initial infection.^1,8

Conclusion

The contagious hand pustule caused by orf virus is a distinct clinical entity that is prevalent worldwide and requires thorough evaluation of the clinical course of the lesion and the patient’s social history. Several zoonotic viral infections have been implicated in this presentation. Although biopsy and molecular studies can be helpful, the expert diagnostician can make a clinical diagnosis with careful attention to social history, geographic location, and cultural practices.

A patient presenting with a hand pustule is a phenomenon encountered worldwide requiring careful history-taking. Some occupations, activities, and various religious practices (eg, Eid al-Adha, Passover, Easter) have been implicated worldwide in orf infection. In the United States, orf virus usually is spread from infected animal hosts to humans. Herein, we review the differential for a single hand pustule, which includes both infectious and noninfectious causes. Recognizing orf virus as the etiology of a cutaneous hand pustule in patients is important, as misdiagnosis can lead to unnecessary invasive testing and/or treatments with suboptimal clinical outcomes.

Case Series

When conducting a search for orf virus cases at our institution (University of Iowa Hospitals and Clinics, Iowa City, Iowa), 5 patient cases were identified.

Patient 1—A 27-year-old otherwise healthy woman presented to clinic with a tender red bump on the right ring finger that had been slowly growing over the course of 2 weeks and had recently started to bleed. A social history revealed that she owned several goats, which she frequently milked; 1 of the goats had a cyst on the mouth, which she popped approximately 1 to 2 weeks prior to the appearance of the lesion on the finger. She also endorsed that she owned several cattle and various other animals with which she had frequent contact. A biopsy was obtained with features consistent with orf virus.

Patient 2—A 33-year-old man presented to clinic with a lesion of concern on the left index finger. Several days prior to presentation, the patient had visited the emergency department for swelling and erythema of the same finger after cutting himself with a knife while preparing sheep meat. Radiographs were normal, and the patient was referred to dermatology. In clinic, there was a 0.5-cm fluctuant mass on the distal interphalangeal joint of the third finger. The patient declined a biopsy, and the lesion healed over 4 to 6 weeks without complication.

Patient 3—A 38-year-old man presented to clinic with 2 painless, large, round nodules on the right proximal index finger, with open friable centers noted on physical examination (Figure 1). The patient reported cutting the finger while preparing sheep meat several days prior. The nodules had been present for a few weeks and continued to grow. A punch biopsy revealed evidence of parapoxvirus infection consistent with a diagnosis of orf.

Patient 4—A 48-year-old man was referred to our dermatology clinic for evaluation of a bleeding lesion on the left middle finger. Physical examination revealed an exophytic, friable, ulcerated nodule on the dorsal aspect of the left middle finger (Figure 2). Upon further questioning, the patient mentioned that he handled raw lamb meat after cutting the finger. A punch biopsy was obtained and was consistent with orf virus infection.

Patient 5—A 43-year-old woman presented to clinic with a chronic wound on the mid lower back that was noted to drain and crust over. She thought the lesion was improving, but it had become painful over the last few weeks. A shave biopsy of the lesion was consistent with orf virus. At follow-up, the patient was unable to identify any recent contact with animals.

Transmission From Animals to Humans—Orf virus is a member of the Parapoxvirus genus of the Poxviridae family.¹ This virus is highly contagious among animals and has been described around the globe. The resulting disease also is known as contagious pustular dermatitis,² soremuzzle,³ ecthyma contagiosum of sheep,⁴ and scabby mouth.⁵ This virus most commonly infects young lambs and manifests as raw to crusty papules, pustules, or vesicles around the mouth and nose of the animal.⁴ Additional signs include excessive salivation and weight loss or starvation from the inability to suckle because of the lesions.⁵ Although ecthyma contagiosum infection of sheep and goats has been well known for centuries, human infection was first reported in the literature in 1934.⁶

Transmission of orf to humans can occur when direct contact with an infected animal exhibiting active lesions occurs.⁷ Orf virus also can be transmitted through fomites (eg, from knives, wool, buildings, equipment) that previously were in contact with infected animals, making it relevant to ask all farmers about any animals with pustules around the mouth, nose, udders, or other commonly affected areas. Although sanitation efforts are important for prevention, orf virus is hardy, and fomites can remain on surfaces for many months.⁸ Transmission among animals and from animals to humans frequently occurs; however, human-to-human transmission is less common.⁹ Ecthyma contagiosum is considered an occupational hazard, with the disease being most prevalent in shepherds, veterinarians, and butchers.^1,8 Disease prevalence in these occupations has been reported to be as high as 50%.¹⁰ Infections also are seen in patients who attend petting zoos or who slaughter goats and sheep for cultural practices.⁸

Clinical Characteristics in Humans—The clinical diagnosis of orf is dependent on taking a thorough patient history that includes social, occupational, and religious activities. Development of a nodule or papule on a patient’s hand with recent exposure to fomites or direct contact with a goat or sheep up to 1 week prior is extremely suggestive of an orf virus infection.

Clinically, orf most often begins as an individual papule or nodule on the dorsal surface of the patient’s finger or hand and ranges from completely asymptomatic to pruritic or even painful.^1,8 Depending on how the infection was inoculated, lesions can vary in size and number. Other sites that have been reported less frequently include the genitals, legs, axillae, and head.^11,12 Lesions are roughly 1 cm in diameter but can vary in size. Ecthyma contagiosum is not a static disease but changes in appearance over the course of infection. Typically, lesions will appear 3 to 7 days after inoculation with the orf virus and will self-resolve 6 to 8 weeks later.

Orf lesions have been described to progress through 6 distinct phases before resolving: maculopapular (erythematous macule or papule forms), targetoid (formation of a necrotic center with red outer halo), acute (lesion begins to weep), regenerative (lesion becomes dry), papilloma (dry crust becomes papillomatous), and regression (skin returns to normal appearance).^1,8,9 Each phase of ecthyma contagiosum is unique and will last up to 1 week before progressing. Because of this prolonged clinical course, patients can present at any stage.

Reports of systemic symptoms are uncommon but can include lymphadenopathy, fever, and malaise.¹³ Although the disease course in immunocompetent individuals is quite mild, immunocompromised patients may experience persistent orf lesions that are painful and can be much larger, with reports of several centimeters in diameter.¹⁴

Dermatopathology and Molecular Studies—When a clinical diagnosis is not possible, biopsy or molecular studies can be helpful.⁸ Histopathology can vary depending on the phase of the lesion. Early stages are characterized by spongiform degeneration of the epidermis with variable vesiculation of the superficial epidermis and eosinophilic cytoplasmic inclusion bodies of keratinocytes (Figure 3). Later stages demonstrate full-thickness necrosis with epidermal balloon degeneration and dense inflammation of the dermis with edema and extravasated erythrocytes from dilated blood vessels. Both early- and late-stage disease commonly show characteristic elongated thin rete ridges.⁸

Molecular studies are another reliable method for diagnosis, though these are not always readily available. Polymerase chain reaction can be used for sensitive and rapid diagnosis.¹⁵ Less commonly, electron microscopy, Western blot, or enzyme-linked immunosorbent assays are used.¹⁶ Laboratory studies, such as complete blood cell count with differential, erythrocyte sedimentation rate, and C-reactive protein, often are unnecessary but may be helpful in ruling out other infectious causes. Tissue culture can be considered if bacterial, fungal, or acid-fast bacilli are in the differential; however, no growth will be seen in the case of orf viral infection.

Differential Diagnosis—The differential diagnosis for patients presenting with a large pustule on the hand or fingers can depend on geographic location, as the potential etiology may vary widely around the world. Several zoonotic viral infections other than orf can present with pustular lesions on the hands (Table).^17-24

Clinically, infection with these named viruses can be hard to distinguish; however, appropriate social history or polymerase chain reaction can be obtained to differentiate them. Other infectious entities include herpetic whitlow, giant molluscum, and anthrax (eTable).^24-26 Biopsy of the lesion with bacterial tissue culture may lead to definitive diagnosis.²⁶

Treatment—Because of the self-resolving nature of orf, treatment usually is not needed in immunocompetent patients with a solitary lesion. However, wound care is essential to prevent secondary infections of the lesion. If secondarily infected, topical or oral antibiotics may be prescribed. Immunocompromised individuals are at increased risk for developing large persistent lesions and sometimes require intervention for successful treatment. Several successful treatment methods have been described and include intralesional interferon injections, electrocautery, topical imiquimod, topical cidofovir, and cryotherapy.^8,14,27-30 Infections that continue to be refractory to less-invasive treatment can be considered for wide local excision; however, recurrence is possible.⁸ Vaccinations are available for animals to prevent the spread of infection in the flock, but there are no formulations of vaccines for human use. Prevention of spread to humans can be done through animal vaccination, careful handling of animal products while wearing nonporous gloves, and proper sanitation techniques.

Complications—Orf has an excellent long-term prognosis in immunocompetent patients, as the virus is epitheliotropic, and inoculation does not lead to viremia.² Although lesions typically are asymptomatic in most patients, complications can occur, especially in immunosuppressed individuals. These complications include systemic symptoms, giant persistent lesions prone to infection or scarring, erysipelas, lymphadenitis, and erythema multiforme.^8,31 Common systemic symptoms of ecthyma contagiosum include fever, fatigue, and myalgia. Lymphadenitis can occur along with local swelling and lymphatic streaking. Although erythema multiforme is a rare complication occurring after initial ecthyma contagiosum infection, this hypersensitivity reaction is postulated to be in response to the immunologic clearing of the orf virus.^32,33 Patients receiving systemic immunosuppressive medications are at an increased risk of developing complications from infection and may even be required to pause systemic treatment for complete resolution of orf lesions.³⁴ Other cutaneous diseases that decrease the skin’s barrier protection, such as bullous pemphigoid or eczema, also can place patients at an increased risk for complications.³⁵ Although human-to-human orf virus transmission is exceptionally rare, there is a case report of this phenomenon in immunosuppressed patients residing in a burn unit.³⁶ Transplant recipients on immunosuppressive medications also can experience orf lesions with exaggerated presentations that continue to grow up to several centimeters in diameter.³¹ Long-term prognosis is still good in these patients with appropriate disease recognition and treatment. Reinfection is not uncommon with repeated exposure to the source, but lesions are less severe and resolve faster than with initial infection.^1,8

Conclusion

The contagious hand pustule caused by orf virus is a distinct clinical entity that is prevalent worldwide and requires thorough evaluation of the clinical course of the lesion and the patient’s social history. Several zoonotic viral infections have been implicated in this presentation. Although biopsy and molecular studies can be helpful, the expert diagnostician can make a clinical diagnosis with careful attention to social history, geographic location, and cultural practices.

Case Report

A 77-year-old man was admitted to the general medicine service at our institution for treatment of a diffuse macular eruption and hemorrhagic bullae 12 days after undergoing left-knee revision arthroplasty during which a cement spacer impregnated with vancomycin and tobramycin was placed. At the time of the surgery, the patient also received intravenous (IV) vancomycin and oral ciprofloxacin, which were continued postoperatively until his hospital presentation. The patient was recovering well until postoperative day 7, when he developed painful swelling and erythema surrounding the surgical wound on the left knee. Concerned that his symptoms indicated a flare of gout, he restarted a former allopurinol prescription from an outside physician after 2 years of nonuse. The skin changes progressed distally on the left leg over the next 48 hours. By postoperative day 10, he had developed serosanguinous blisters on the left knee (Figure 1A) and oral mucosa (Figure 1B), as well as erythematous nodules on the bilateral palms. He presented to our institution for emergent care on postoperative day 12 following progression of the eruption to the inguinal region (Figure 2A), buttocks (Figure 2B), and abdominal region.

Due to concerns about a potential drug reaction, the IV vancomycin, oral ciprofloxacin, and oral allopurinol were discontinued on hospital admission. A dermatology consultation (D.A.D., J.A.Z., E.T.) was obtained, and a punch biopsy from a lesion on the left thigh revealed a neutrophil-rich subepidermal bulla with scattered eosinophils (Figure 3A). Direct immunofluorescence demonstrated linear IgA (Figure 3B) and C3 deposition along the dermoepidermal junction, which confirmed a diagnosis of drug-induced linear IgA bullous dermatosis (LABD). Vancomycin was suspected as the causative agent.¹ An initial vancomycin trough level drawn 48 hours after discontinuation (postoperative day 13) was still therapeutic at 14 µg/mL (reference range, 10–20 µg/mL in adults). This was substantially higher than the predicted value of 3 µg/mL based on renal excretion. Similarly, 5 additional serum levels obtained during the patient’s hospital course were greater than those predicted, and follow-up trough levels remained detectable at 1 µg/mL 2 weeks after discontinuation.

Oral prednisone 60 mg once daily and oral dapsone 25 mg once daily were initiated on hospital days 4 and 6 (postoperative days 15 and 17), respectively. A 6-week course of oral ciprofloxacin 750 mg twice daily and daptomycin 8 mg/kg once daily was initiated for bacterial coverage on hospital day 5 (postoperative day 16). Topical triamcinolone and an anesthetic mouthwash also were used to treat the mucosal involvement. The lesions stabilized on the third day of steroid therapy, and the patient was discharged 7 days after hospital admission (postoperative day 18). Dapsone was rapidly increased to 100 mg once daily over the next week for Pneumocystis jirovecii pneumonia prophylaxis. An increase in prednisone to 80 mg once daily was required 3 days after the patient was discharged due to worsening oral lesions. Five days after discharge, the patient was readmitted to the hospital for 3 days due to acute kidney injury (AKI) in which his baseline creatinine level tripled. The cause of renal impairment was unknown, resulting in empiric discontinuation of dapsone on postoperative day 27. Prophylaxis for P jirovecii pneumonia was replaced with once-monthly inhaled pentamidine. Prednisone was tapered 20 days after the original presentation (postoperative day 32) following gradual improvement of both the skin and oral lesions. At dermatology follow-up 2 weeks later, doxycycline 100 mg twice daily was added for residual inflammation of the left leg. A deep vein thrombosis was discovered in the left leg 10 days later, and 3 months of anticoagulation therapy was initiated with discontinuation of the doxycycline. The patient continued to have renal insufficiency several weeks after dapsone discontinuation and developed prominent peripheral motor neuropathy with bilateral thenar atrophy. He did not experience any skin eruptions or relapses in the weeks following prednisone cessation and underwent successful removal of the cement spacer with full left-knee reconstruction 4 months after his initial presentation to our institution. At 9-month dermatology follow-up, the LABD remained in remission.

Comment

Linear IgA bullous dermatosis is a well-documented autoimmune mucocutaneous disorder characterized by linear IgA deposits at the dermoepidermal junction. The development of autoantibodies to antigens within the basement membrane zone leads to both cellular and humoral immune responses that facilitate the subepidermal blistering rash in LABD.^2,3 Linear IgA bullous dermatosis affects all ages and races with a bimodal epidemiology. The adult form typically appears after 60 years of age, whereas the childhood form (chronic bullous disease of childhood) appears between 6 months and 6 years of age.³ Medications—particularly vancomycin—are responsible for a substantial portion of cases.^1-4 In one review, vancomycin was implicated in almost half (22/52 [42.3%]) of drug-related cases of LABD.⁴ Other associated medications include captopril, trimethoprim-sulfamethoxazole, phenytoin, and diclo-fenac.^3,4 Vancomycin-associated LABD has a substantially shorter time to onset of symptoms, with a mean of 8.6 days compared to 63.8 days for other causative agents.⁴Resolution of symptoms also occurs more quickly, with remission occurring in 66.7% (16/24) of cases at a mean time of 13 days compared to a 39.2% (11/28) resolution rate with a mean time of 18.9 days following discontinuation of other implicated medications.⁴ While idiopathic LABD involves the mucous membranes in up to 80% of cases, drug-induced LABD is less commonly associated with mucosal lesions. In an earlier systematic review from 1966 to 2002, 32% (7/22) of reported cases of vancomycin-induced LABD were reported to have mucosal involvement.^5,6 In 2012, one group found that most published cases of drug-induced LABD do not use standardized algorithms, such as the Naranjo algorithm, to definitively tie LABD onset to medication use.⁴ The Naranjo algorithm, devised in 1981, consists of 10 questions that determine the probability of adverse drug reactions.⁷ In our case, a Naranjo score of 5 suggested a probable adverse drug reaction due to vancomycin use; however, we cannot completely exclude ciprofloxacin in our case in light of a case report of LABD in the setting of IV vancomycin and ciprofloxacin use.⁸ In our patient, ciprofloxacin had a Naranjo score of 2, which suggested a possible adverse drug reaction. Allopurinol, which does not have any published association with LABD, also had a Naranjo score of 2 in our patient.

The initial treatment of drug-induced LABD is immediate discontinuation of the suspected agent(s) and supportive care.⁹ Although future avoidance of vancomycin is recommended in patients with a history of LABD, there are reported cases of successful rechallenges.^4,10 The early removal of our patient’s cement spacer was discouraged by both the orthopedics and infectious disease consultation services due to potential complications as well as the patient’s gradual improvement during his hospital course.

Dapsone is considered the standard systemic treatment for LABD. Sulfapyridine is an alternative to dapsone, or a combination of these 2 drugs may be used. Corticosteroids can be added to each of these regimens to achieve remission, as in our case.² Although dapsone was discontinued in the setting of the patient’s AKI, the vancomycin in the dual-eluting spacer was more likely the culprit. A review of 544 postoperative outcomes following the use of an antibiotic-impregnated cement spacer (AICS) during 2-stage arthroplasty displayed an 8- to 10-fold increase in the development of AKIs compared to the rate of AKIs following primary joint arthroplasty.¹⁰ While our patient’s AKI was not attributed to dapsone, his prominent peripheral motor neuropathy with resultant bilateral thenar atrophy was a rare complication of dapsone use. While dapsone-associated neuropathy has been reported in daily dosages of as low as 75 mg, it typically is seen in doses of at least 300 mg per day and in larger cumulative dosages.¹¹

Despite having a well-characterized vancomycin-induced LABD in the setting of known vancomycin exposure, our patient’s case was particularly challenging given the continued presence of the vancomycin-impregnated cement spacer (VICS) in the left knee, resulting in vancomycin levels at admission and during subsequent measurements over 2 weeks that were all several-fold higher than the renal clearance predicted.

Vancomycin-associated LABD does not appear to be dose dependent and has been reported at both subtherapeutic^1-3 and supratherapeutic levels,^5-9 whereas toxicity reactions are more common at supratherapeutic levels.⁹ The literature on AICS use suggests that drug elution occurs at relatively unpredictable rates based on a variety of factors, including the type of cement used and the initial antibiotic concentration.^12,13 Furthermore, the addition of tobramycin to VICSs has been found to increase the rate of vancomycin delivery through a phenomenon known as passive opportunism.¹⁴

As AICS devices allow for the delivery of higher concentrations of antibiotics to a localized area, systemic complications are considered rare but have been reported.¹³ Our report describes a rare case of LABD in the setting of a VICS. One clinical aspect of our case that supports the implication of VICS as the cause of the patient’s LABD is the concentration of bullae overlying the incision site on the left knee. A case of a desquamating rash in a patient with an implanted VICS has been documented in which the early lesions were localized to the surgical leg, as in our case.¹⁵ Unlike our case, there was a history of Stevens-Johnson syndrome following previous vancomycin exposure. A case of a gentamicin-impregnated cement spacer causing allergic dermatitis that was most prominent in the surgical leg also has been reported.¹⁶ An isomorphic phenomenon (Köbner phenomenon) has been suggested in the setting of vancomycin-induced LABD lesions that intensified at a site of adhesive tape application,¹⁷ but the Köbner phenomenon did not appear to be a major factor in our patient. The removal of the patient’s cement spacer was performed to prevent development of a chronic autoimmune response or autoreactivity state against the skin basement membrane zone structural antigen.

Case Report

A 77-year-old man was admitted to the general medicine service at our institution for treatment of a diffuse macular eruption and hemorrhagic bullae 12 days after undergoing left-knee revision arthroplasty during which a cement spacer impregnated with vancomycin and tobramycin was placed. At the time of the surgery, the patient also received intravenous (IV) vancomycin and oral ciprofloxacin, which were continued postoperatively until his hospital presentation. The patient was recovering well until postoperative day 7, when he developed painful swelling and erythema surrounding the surgical wound on the left knee. Concerned that his symptoms indicated a flare of gout, he restarted a former allopurinol prescription from an outside physician after 2 years of nonuse. The skin changes progressed distally on the left leg over the next 48 hours. By postoperative day 10, he had developed serosanguinous blisters on the left knee (Figure 1A) and oral mucosa (Figure 1B), as well as erythematous nodules on the bilateral palms. He presented to our institution for emergent care on postoperative day 12 following progression of the eruption to the inguinal region (Figure 2A), buttocks (Figure 2B), and abdominal region.

Due to concerns about a potential drug reaction, the IV vancomycin, oral ciprofloxacin, and oral allopurinol were discontinued on hospital admission. A dermatology consultation (D.A.D., J.A.Z., E.T.) was obtained, and a punch biopsy from a lesion on the left thigh revealed a neutrophil-rich subepidermal bulla with scattered eosinophils (Figure 3A). Direct immunofluorescence demonstrated linear IgA (Figure 3B) and C3 deposition along the dermoepidermal junction, which confirmed a diagnosis of drug-induced linear IgA bullous dermatosis (LABD). Vancomycin was suspected as the causative agent.¹ An initial vancomycin trough level drawn 48 hours after discontinuation (postoperative day 13) was still therapeutic at 14 µg/mL (reference range, 10–20 µg/mL in adults). This was substantially higher than the predicted value of 3 µg/mL based on renal excretion. Similarly, 5 additional serum levels obtained during the patient’s hospital course were greater than those predicted, and follow-up trough levels remained detectable at 1 µg/mL 2 weeks after discontinuation.

Oral prednisone 60 mg once daily and oral dapsone 25 mg once daily were initiated on hospital days 4 and 6 (postoperative days 15 and 17), respectively. A 6-week course of oral ciprofloxacin 750 mg twice daily and daptomycin 8 mg/kg once daily was initiated for bacterial coverage on hospital day 5 (postoperative day 16). Topical triamcinolone and an anesthetic mouthwash also were used to treat the mucosal involvement. The lesions stabilized on the third day of steroid therapy, and the patient was discharged 7 days after hospital admission (postoperative day 18). Dapsone was rapidly increased to 100 mg once daily over the next week for Pneumocystis jirovecii pneumonia prophylaxis. An increase in prednisone to 80 mg once daily was required 3 days after the patient was discharged due to worsening oral lesions. Five days after discharge, the patient was readmitted to the hospital for 3 days due to acute kidney injury (AKI) in which his baseline creatinine level tripled. The cause of renal impairment was unknown, resulting in empiric discontinuation of dapsone on postoperative day 27. Prophylaxis for P jirovecii pneumonia was replaced with once-monthly inhaled pentamidine. Prednisone was tapered 20 days after the original presentation (postoperative day 32) following gradual improvement of both the skin and oral lesions. At dermatology follow-up 2 weeks later, doxycycline 100 mg twice daily was added for residual inflammation of the left leg. A deep vein thrombosis was discovered in the left leg 10 days later, and 3 months of anticoagulation therapy was initiated with discontinuation of the doxycycline. The patient continued to have renal insufficiency several weeks after dapsone discontinuation and developed prominent peripheral motor neuropathy with bilateral thenar atrophy. He did not experience any skin eruptions or relapses in the weeks following prednisone cessation and underwent successful removal of the cement spacer with full left-knee reconstruction 4 months after his initial presentation to our institution. At 9-month dermatology follow-up, the LABD remained in remission.

Comment

Linear IgA bullous dermatosis is a well-documented autoimmune mucocutaneous disorder characterized by linear IgA deposits at the dermoepidermal junction. The development of autoantibodies to antigens within the basement membrane zone leads to both cellular and humoral immune responses that facilitate the subepidermal blistering rash in LABD.^2,3 Linear IgA bullous dermatosis affects all ages and races with a bimodal epidemiology. The adult form typically appears after 60 years of age, whereas the childhood form (chronic bullous disease of childhood) appears between 6 months and 6 years of age.³ Medications—particularly vancomycin—are responsible for a substantial portion of cases.^1-4 In one review, vancomycin was implicated in almost half (22/52 [42.3%]) of drug-related cases of LABD.⁴ Other associated medications include captopril, trimethoprim-sulfamethoxazole, phenytoin, and diclo-fenac.^3,4 Vancomycin-associated LABD has a substantially shorter time to onset of symptoms, with a mean of 8.6 days compared to 63.8 days for other causative agents.⁴Resolution of symptoms also occurs more quickly, with remission occurring in 66.7% (16/24) of cases at a mean time of 13 days compared to a 39.2% (11/28) resolution rate with a mean time of 18.9 days following discontinuation of other implicated medications.⁴ While idiopathic LABD involves the mucous membranes in up to 80% of cases, drug-induced LABD is less commonly associated with mucosal lesions. In an earlier systematic review from 1966 to 2002, 32% (7/22) of reported cases of vancomycin-induced LABD were reported to have mucosal involvement.^5,6 In 2012, one group found that most published cases of drug-induced LABD do not use standardized algorithms, such as the Naranjo algorithm, to definitively tie LABD onset to medication use.⁴ The Naranjo algorithm, devised in 1981, consists of 10 questions that determine the probability of adverse drug reactions.⁷ In our case, a Naranjo score of 5 suggested a probable adverse drug reaction due to vancomycin use; however, we cannot completely exclude ciprofloxacin in our case in light of a case report of LABD in the setting of IV vancomycin and ciprofloxacin use.⁸ In our patient, ciprofloxacin had a Naranjo score of 2, which suggested a possible adverse drug reaction. Allopurinol, which does not have any published association with LABD, also had a Naranjo score of 2 in our patient.

The initial treatment of drug-induced LABD is immediate discontinuation of the suspected agent(s) and supportive care.⁹ Although future avoidance of vancomycin is recommended in patients with a history of LABD, there are reported cases of successful rechallenges.^4,10 The early removal of our patient’s cement spacer was discouraged by both the orthopedics and infectious disease consultation services due to potential complications as well as the patient’s gradual improvement during his hospital course.

Dapsone is considered the standard systemic treatment for LABD. Sulfapyridine is an alternative to dapsone, or a combination of these 2 drugs may be used. Corticosteroids can be added to each of these regimens to achieve remission, as in our case.² Although dapsone was discontinued in the setting of the patient’s AKI, the vancomycin in the dual-eluting spacer was more likely the culprit. A review of 544 postoperative outcomes following the use of an antibiotic-impregnated cement spacer (AICS) during 2-stage arthroplasty displayed an 8- to 10-fold increase in the development of AKIs compared to the rate of AKIs following primary joint arthroplasty.¹⁰ While our patient’s AKI was not attributed to dapsone, his prominent peripheral motor neuropathy with resultant bilateral thenar atrophy was a rare complication of dapsone use. While dapsone-associated neuropathy has been reported in daily dosages of as low as 75 mg, it typically is seen in doses of at least 300 mg per day and in larger cumulative dosages.¹¹

Despite having a well-characterized vancomycin-induced LABD in the setting of known vancomycin exposure, our patient’s case was particularly challenging given the continued presence of the vancomycin-impregnated cement spacer (VICS) in the left knee, resulting in vancomycin levels at admission and during subsequent measurements over 2 weeks that were all several-fold higher than the renal clearance predicted.

Vancomycin-associated LABD does not appear to be dose dependent and has been reported at both subtherapeutic^1-3 and supratherapeutic levels,^5-9 whereas toxicity reactions are more common at supratherapeutic levels.⁹ The literature on AICS use suggests that drug elution occurs at relatively unpredictable rates based on a variety of factors, including the type of cement used and the initial antibiotic concentration.^12,13 Furthermore, the addition of tobramycin to VICSs has been found to increase the rate of vancomycin delivery through a phenomenon known as passive opportunism.¹⁴

As AICS devices allow for the delivery of higher concentrations of antibiotics to a localized area, systemic complications are considered rare but have been reported.¹³ Our report describes a rare case of LABD in the setting of a VICS. One clinical aspect of our case that supports the implication of VICS as the cause of the patient’s LABD is the concentration of bullae overlying the incision site on the left knee. A case of a desquamating rash in a patient with an implanted VICS has been documented in which the early lesions were localized to the surgical leg, as in our case.¹⁵ Unlike our case, there was a history of Stevens-Johnson syndrome following previous vancomycin exposure. A case of a gentamicin-impregnated cement spacer causing allergic dermatitis that was most prominent in the surgical leg also has been reported.¹⁶ An isomorphic phenomenon (Köbner phenomenon) has been suggested in the setting of vancomycin-induced LABD lesions that intensified at a site of adhesive tape application,¹⁷ but the Köbner phenomenon did not appear to be a major factor in our patient. The removal of the patient’s cement spacer was performed to prevent development of a chronic autoimmune response or autoreactivity state against the skin basement membrane zone structural antigen.

Case Report

A 77-year-old man was admitted to the general medicine service at our institution for treatment of a diffuse macular eruption and hemorrhagic bullae 12 days after undergoing left-knee revision arthroplasty during which a cement spacer impregnated with vancomycin and tobramycin was placed. At the time of the surgery, the patient also received intravenous (IV) vancomycin and oral ciprofloxacin, which were continued postoperatively until his hospital presentation. The patient was recovering well until postoperative day 7, when he developed painful swelling and erythema surrounding the surgical wound on the left knee. Concerned that his symptoms indicated a flare of gout, he restarted a former allopurinol prescription from an outside physician after 2 years of nonuse. The skin changes progressed distally on the left leg over the next 48 hours. By postoperative day 10, he had developed serosanguinous blisters on the left knee (Figure 1A) and oral mucosa (Figure 1B), as well as erythematous nodules on the bilateral palms. He presented to our institution for emergent care on postoperative day 12 following progression of the eruption to the inguinal region (Figure 2A), buttocks (Figure 2B), and abdominal region.

Due to concerns about a potential drug reaction, the IV vancomycin, oral ciprofloxacin, and oral allopurinol were discontinued on hospital admission. A dermatology consultation (D.A.D., J.A.Z., E.T.) was obtained, and a punch biopsy from a lesion on the left thigh revealed a neutrophil-rich subepidermal bulla with scattered eosinophils (Figure 3A). Direct immunofluorescence demonstrated linear IgA (Figure 3B) and C3 deposition along the dermoepidermal junction, which confirmed a diagnosis of drug-induced linear IgA bullous dermatosis (LABD). Vancomycin was suspected as the causative agent.¹ An initial vancomycin trough level drawn 48 hours after discontinuation (postoperative day 13) was still therapeutic at 14 µg/mL (reference range, 10–20 µg/mL in adults). This was substantially higher than the predicted value of 3 µg/mL based on renal excretion. Similarly, 5 additional serum levels obtained during the patient’s hospital course were greater than those predicted, and follow-up trough levels remained detectable at 1 µg/mL 2 weeks after discontinuation.

Oral prednisone 60 mg once daily and oral dapsone 25 mg once daily were initiated on hospital days 4 and 6 (postoperative days 15 and 17), respectively. A 6-week course of oral ciprofloxacin 750 mg twice daily and daptomycin 8 mg/kg once daily was initiated for bacterial coverage on hospital day 5 (postoperative day 16). Topical triamcinolone and an anesthetic mouthwash also were used to treat the mucosal involvement. The lesions stabilized on the third day of steroid therapy, and the patient was discharged 7 days after hospital admission (postoperative day 18). Dapsone was rapidly increased to 100 mg once daily over the next week for Pneumocystis jirovecii pneumonia prophylaxis. An increase in prednisone to 80 mg once daily was required 3 days after the patient was discharged due to worsening oral lesions. Five days after discharge, the patient was readmitted to the hospital for 3 days due to acute kidney injury (AKI) in which his baseline creatinine level tripled. The cause of renal impairment was unknown, resulting in empiric discontinuation of dapsone on postoperative day 27. Prophylaxis for P jirovecii pneumonia was replaced with once-monthly inhaled pentamidine. Prednisone was tapered 20 days after the original presentation (postoperative day 32) following gradual improvement of both the skin and oral lesions. At dermatology follow-up 2 weeks later, doxycycline 100 mg twice daily was added for residual inflammation of the left leg. A deep vein thrombosis was discovered in the left leg 10 days later, and 3 months of anticoagulation therapy was initiated with discontinuation of the doxycycline. The patient continued to have renal insufficiency several weeks after dapsone discontinuation and developed prominent peripheral motor neuropathy with bilateral thenar atrophy. He did not experience any skin eruptions or relapses in the weeks following prednisone cessation and underwent successful removal of the cement spacer with full left-knee reconstruction 4 months after his initial presentation to our institution. At 9-month dermatology follow-up, the LABD remained in remission.

Comment

Linear IgA bullous dermatosis is a well-documented autoimmune mucocutaneous disorder characterized by linear IgA deposits at the dermoepidermal junction. The development of autoantibodies to antigens within the basement membrane zone leads to both cellular and humoral immune responses that facilitate the subepidermal blistering rash in LABD.^2,3 Linear IgA bullous dermatosis affects all ages and races with a bimodal epidemiology. The adult form typically appears after 60 years of age, whereas the childhood form (chronic bullous disease of childhood) appears between 6 months and 6 years of age.³ Medications—particularly vancomycin—are responsible for a substantial portion of cases.^1-4 In one review, vancomycin was implicated in almost half (22/52 [42.3%]) of drug-related cases of LABD.⁴ Other associated medications include captopril, trimethoprim-sulfamethoxazole, phenytoin, and diclo-fenac.^3,4 Vancomycin-associated LABD has a substantially shorter time to onset of symptoms, with a mean of 8.6 days compared to 63.8 days for other causative agents.⁴Resolution of symptoms also occurs more quickly, with remission occurring in 66.7% (16/24) of cases at a mean time of 13 days compared to a 39.2% (11/28) resolution rate with a mean time of 18.9 days following discontinuation of other implicated medications.⁴ While idiopathic LABD involves the mucous membranes in up to 80% of cases, drug-induced LABD is less commonly associated with mucosal lesions. In an earlier systematic review from 1966 to 2002, 32% (7/22) of reported cases of vancomycin-induced LABD were reported to have mucosal involvement.^5,6 In 2012, one group found that most published cases of drug-induced LABD do not use standardized algorithms, such as the Naranjo algorithm, to definitively tie LABD onset to medication use.⁴ The Naranjo algorithm, devised in 1981, consists of 10 questions that determine the probability of adverse drug reactions.⁷ In our case, a Naranjo score of 5 suggested a probable adverse drug reaction due to vancomycin use; however, we cannot completely exclude ciprofloxacin in our case in light of a case report of LABD in the setting of IV vancomycin and ciprofloxacin use.⁸ In our patient, ciprofloxacin had a Naranjo score of 2, which suggested a possible adverse drug reaction. Allopurinol, which does not have any published association with LABD, also had a Naranjo score of 2 in our patient.

The initial treatment of drug-induced LABD is immediate discontinuation of the suspected agent(s) and supportive care.⁹ Although future avoidance of vancomycin is recommended in patients with a history of LABD, there are reported cases of successful rechallenges.^4,10 The early removal of our patient’s cement spacer was discouraged by both the orthopedics and infectious disease consultation services due to potential complications as well as the patient’s gradual improvement during his hospital course.

Dapsone is considered the standard systemic treatment for LABD. Sulfapyridine is an alternative to dapsone, or a combination of these 2 drugs may be used. Corticosteroids can be added to each of these regimens to achieve remission, as in our case.² Although dapsone was discontinued in the setting of the patient’s AKI, the vancomycin in the dual-eluting spacer was more likely the culprit. A review of 544 postoperative outcomes following the use of an antibiotic-impregnated cement spacer (AICS) during 2-stage arthroplasty displayed an 8- to 10-fold increase in the development of AKIs compared to the rate of AKIs following primary joint arthroplasty.¹⁰ While our patient’s AKI was not attributed to dapsone, his prominent peripheral motor neuropathy with resultant bilateral thenar atrophy was a rare complication of dapsone use. While dapsone-associated neuropathy has been reported in daily dosages of as low as 75 mg, it typically is seen in doses of at least 300 mg per day and in larger cumulative dosages.¹¹

Despite having a well-characterized vancomycin-induced LABD in the setting of known vancomycin exposure, our patient’s case was particularly challenging given the continued presence of the vancomycin-impregnated cement spacer (VICS) in the left knee, resulting in vancomycin levels at admission and during subsequent measurements over 2 weeks that were all several-fold higher than the renal clearance predicted.

Vancomycin-associated LABD does not appear to be dose dependent and has been reported at both subtherapeutic^1-3 and supratherapeutic levels,^5-9 whereas toxicity reactions are more common at supratherapeutic levels.⁹ The literature on AICS use suggests that drug elution occurs at relatively unpredictable rates based on a variety of factors, including the type of cement used and the initial antibiotic concentration.^12,13 Furthermore, the addition of tobramycin to VICSs has been found to increase the rate of vancomycin delivery through a phenomenon known as passive opportunism.¹⁴

As AICS devices allow for the delivery of higher concentrations of antibiotics to a localized area, systemic complications are considered rare but have been reported.¹³ Our report describes a rare case of LABD in the setting of a VICS. One clinical aspect of our case that supports the implication of VICS as the cause of the patient’s LABD is the concentration of bullae overlying the incision site on the left knee. A case of a desquamating rash in a patient with an implanted VICS has been documented in which the early lesions were localized to the surgical leg, as in our case.¹⁵ Unlike our case, there was a history of Stevens-Johnson syndrome following previous vancomycin exposure. A case of a gentamicin-impregnated cement spacer causing allergic dermatitis that was most prominent in the surgical leg also has been reported.¹⁶ An isomorphic phenomenon (Köbner phenomenon) has been suggested in the setting of vancomycin-induced LABD lesions that intensified at a site of adhesive tape application,¹⁷ but the Köbner phenomenon did not appear to be a major factor in our patient. The removal of the patient’s cement spacer was performed to prevent development of a chronic autoimmune response or autoreactivity state against the skin basement membrane zone structural antigen.

The Diagnosis: Acquired Acrodermatitis Enteropathica

Acquired acrodermatitis enteropathica (AAE) is a rare disorder caused by severe zinc deficiency. Although acrodermatitis enteropathica is an autosomal-recessive disorder that typically manifests in infancy, AAE also can result from poor zinc intake, impaired absorption, or accelerated losses. There are reports of AAE in patients with zinc-deficient diets,¹ eating disorders,² bariatric and other gastrointestinal surgeries,³ malabsorptive diseases,⁴ and nephrotic syndrome.⁵

Zinc plays an important role in DNA and RNA synthesis, reactive oxygen species attenuation, and energy metabolism, allowing for proper wound healing, skin differentiation, and proliferation.⁶ Zinc is found in most foods, but animal protein contains higher concentrations (Table).⁷ Approximately 85% of zinc is stored in muscles and bones, with only a small amount of accessible zinc available in the liver. Liver stores can be depleted as quickly as 1 week.⁸ Total parenteral nutrition without trace element supplementation can quickly predispose patients to AAE.

Diagnosis of this condition requires triangulation of clinical presentation, histopathology examination, and laboratory findings. Acrodermatitis enteropathica typically is characterized by dermatitis, diarrhea, and epidermal appendage findings. In its early stages, the dermatitis often manifests with angular cheilitis and paronychia.⁹ Patients then develop erythema, erosions, and occasionally vesicles or psoriasiform plaques in periorificial, perineal, and acral sites (Figure 1). Epidermal appendage effects include generalized alopecia and thinning nails with white transverse ridges. Although dermatologic and gastrointestinal manifestations are the most obvious, severe AAE may cause other symptoms, including mental slowing, hypogonadism, and impaired immune function.⁹

Histopathology of AAE skin lesions is similar to other nutritional deficiencies. Early changes are more specific to deficiency dermatitis and include cytoplasmic pallor and ballooning degeneration of keratinocytes in the stratum spinosum and granulosum.⁹ Necrolysis results in confluent keratinocyte necrosis developing into subcorneal bulla. Later in the disease course, the presentation becomes psoriasiform with keratinocyte dyskeratosis and confluent parakeratosis¹⁰ (Figure 2). Dermal edema with dilated tortuous vessels and a neutrophilic infiltrate may be present throughout disease progression.

Common laboratory abnormalities used to confirm zinc deficiency are decreased plasma zinc and alkaline phosphatase levels. Plasma zinc levels should be drawn after fasting because zinc levels decrease after food intake.⁹ Concurrent albumin levels should be drawn to correct for low levels caused by hypoalbuminemia. Acquired acrodermatitis enteropathica has been seen in patients with only mildly decreased plasma zinc levels or even zinc levels within reference range.¹¹ Alkaline phosphatase metalloenzyme synthesis requires zinc and a decreased level suggests zinc deficiency even with a plasma zinc level within reference range. Alkaline phosphatase levels usually can be ascertained in a matter of hours, while the zinc levels take much longer to result.

Acquired acrodermatitis enteropathica is treated with oral elemental zinc supplementation at 1 to 2 mg/kg daily.¹² Diarrhea typically resolves within 24 hours, but skin lesions heal in 1 to 2 weeks or longer. Although there is no consensus on when to discontinue zinc replacement therapy, therapy generally is not lifelong. Once the patient is zinc replete and the inciting factor has resolved, patients can discontinue supplementation without risk for recurrence.

Trace elements had not been added to our patient’s total parenteral nutrition prior to admission. Basic nutrition laboratory results and zinc levels returned markedly low: 14 μg/dL (reference range, 60–120 μg/dL). Alkaline phosphatase, a zinc-dependent protein, also was low at 12 U/L (reference range, 40–150 U/L). We added trace elements and vitamins and began empiric zinc replacement with 440 mg oral zinc sulfate daily (100 mg elemental zinc). Cephalexin was prescribed for impetiginized skin lesions. The patient noted skin improvement after 3 days on zinc replacement therapy.

The Diagnosis: Acquired Acrodermatitis Enteropathica

Acquired acrodermatitis enteropathica (AAE) is a rare disorder caused by severe zinc deficiency. Although acrodermatitis enteropathica is an autosomal-recessive disorder that typically manifests in infancy, AAE also can result from poor zinc intake, impaired absorption, or accelerated losses. There are reports of AAE in patients with zinc-deficient diets,¹ eating disorders,² bariatric and other gastrointestinal surgeries,³ malabsorptive diseases,⁴ and nephrotic syndrome.⁵

Zinc plays an important role in DNA and RNA synthesis, reactive oxygen species attenuation, and energy metabolism, allowing for proper wound healing, skin differentiation, and proliferation.⁶ Zinc is found in most foods, but animal protein contains higher concentrations (Table).⁷ Approximately 85% of zinc is stored in muscles and bones, with only a small amount of accessible zinc available in the liver. Liver stores can be depleted as quickly as 1 week.⁸ Total parenteral nutrition without trace element supplementation can quickly predispose patients to AAE.

Diagnosis of this condition requires triangulation of clinical presentation, histopathology examination, and laboratory findings. Acrodermatitis enteropathica typically is characterized by dermatitis, diarrhea, and epidermal appendage findings. In its early stages, the dermatitis often manifests with angular cheilitis and paronychia.⁹ Patients then develop erythema, erosions, and occasionally vesicles or psoriasiform plaques in periorificial, perineal, and acral sites (Figure 1). Epidermal appendage effects include generalized alopecia and thinning nails with white transverse ridges. Although dermatologic and gastrointestinal manifestations are the most obvious, severe AAE may cause other symptoms, including mental slowing, hypogonadism, and impaired immune function.⁹

Histopathology of AAE skin lesions is similar to other nutritional deficiencies. Early changes are more specific to deficiency dermatitis and include cytoplasmic pallor and ballooning degeneration of keratinocytes in the stratum spinosum and granulosum.⁹ Necrolysis results in confluent keratinocyte necrosis developing into subcorneal bulla. Later in the disease course, the presentation becomes psoriasiform with keratinocyte dyskeratosis and confluent parakeratosis¹⁰ (Figure 2). Dermal edema with dilated tortuous vessels and a neutrophilic infiltrate may be present throughout disease progression.

Common laboratory abnormalities used to confirm zinc deficiency are decreased plasma zinc and alkaline phosphatase levels. Plasma zinc levels should be drawn after fasting because zinc levels decrease after food intake.⁹ Concurrent albumin levels should be drawn to correct for low levels caused by hypoalbuminemia. Acquired acrodermatitis enteropathica has been seen in patients with only mildly decreased plasma zinc levels or even zinc levels within reference range.¹¹ Alkaline phosphatase metalloenzyme synthesis requires zinc and a decreased level suggests zinc deficiency even with a plasma zinc level within reference range. Alkaline phosphatase levels usually can be ascertained in a matter of hours, while the zinc levels take much longer to result.

Acquired acrodermatitis enteropathica is treated with oral elemental zinc supplementation at 1 to 2 mg/kg daily.¹² Diarrhea typically resolves within 24 hours, but skin lesions heal in 1 to 2 weeks or longer. Although there is no consensus on when to discontinue zinc replacement therapy, therapy generally is not lifelong. Once the patient is zinc replete and the inciting factor has resolved, patients can discontinue supplementation without risk for recurrence.

Trace elements had not been added to our patient’s total parenteral nutrition prior to admission. Basic nutrition laboratory results and zinc levels returned markedly low: 14 μg/dL (reference range, 60–120 μg/dL). Alkaline phosphatase, a zinc-dependent protein, also was low at 12 U/L (reference range, 40–150 U/L). We added trace elements and vitamins and began empiric zinc replacement with 440 mg oral zinc sulfate daily (100 mg elemental zinc). Cephalexin was prescribed for impetiginized skin lesions. The patient noted skin improvement after 3 days on zinc replacement therapy.

The Diagnosis: Acquired Acrodermatitis Enteropathica

Acquired acrodermatitis enteropathica (AAE) is a rare disorder caused by severe zinc deficiency. Although acrodermatitis enteropathica is an autosomal-recessive disorder that typically manifests in infancy, AAE also can result from poor zinc intake, impaired absorption, or accelerated losses. There are reports of AAE in patients with zinc-deficient diets,¹ eating disorders,² bariatric and other gastrointestinal surgeries,³ malabsorptive diseases,⁴ and nephrotic syndrome.⁵

Zinc plays an important role in DNA and RNA synthesis, reactive oxygen species attenuation, and energy metabolism, allowing for proper wound healing, skin differentiation, and proliferation.⁶ Zinc is found in most foods, but animal protein contains higher concentrations (Table).⁷ Approximately 85% of zinc is stored in muscles and bones, with only a small amount of accessible zinc available in the liver. Liver stores can be depleted as quickly as 1 week.⁸ Total parenteral nutrition without trace element supplementation can quickly predispose patients to AAE.

Diagnosis of this condition requires triangulation of clinical presentation, histopathology examination, and laboratory findings. Acrodermatitis enteropathica typically is characterized by dermatitis, diarrhea, and epidermal appendage findings. In its early stages, the dermatitis often manifests with angular cheilitis and paronychia.⁹ Patients then develop erythema, erosions, and occasionally vesicles or psoriasiform plaques in periorificial, perineal, and acral sites (Figure 1). Epidermal appendage effects include generalized alopecia and thinning nails with white transverse ridges. Although dermatologic and gastrointestinal manifestations are the most obvious, severe AAE may cause other symptoms, including mental slowing, hypogonadism, and impaired immune function.⁹

Histopathology of AAE skin lesions is similar to other nutritional deficiencies. Early changes are more specific to deficiency dermatitis and include cytoplasmic pallor and ballooning degeneration of keratinocytes in the stratum spinosum and granulosum.⁹ Necrolysis results in confluent keratinocyte necrosis developing into subcorneal bulla. Later in the disease course, the presentation becomes psoriasiform with keratinocyte dyskeratosis and confluent parakeratosis¹⁰ (Figure 2). Dermal edema with dilated tortuous vessels and a neutrophilic infiltrate may be present throughout disease progression.

Common laboratory abnormalities used to confirm zinc deficiency are decreased plasma zinc and alkaline phosphatase levels. Plasma zinc levels should be drawn after fasting because zinc levels decrease after food intake.⁹ Concurrent albumin levels should be drawn to correct for low levels caused by hypoalbuminemia. Acquired acrodermatitis enteropathica has been seen in patients with only mildly decreased plasma zinc levels or even zinc levels within reference range.¹¹ Alkaline phosphatase metalloenzyme synthesis requires zinc and a decreased level suggests zinc deficiency even with a plasma zinc level within reference range. Alkaline phosphatase levels usually can be ascertained in a matter of hours, while the zinc levels take much longer to result.

Acquired acrodermatitis enteropathica is treated with oral elemental zinc supplementation at 1 to 2 mg/kg daily.¹² Diarrhea typically resolves within 24 hours, but skin lesions heal in 1 to 2 weeks or longer. Although there is no consensus on when to discontinue zinc replacement therapy, therapy generally is not lifelong. Once the patient is zinc replete and the inciting factor has resolved, patients can discontinue supplementation without risk for recurrence.

Trace elements had not been added to our patient’s total parenteral nutrition prior to admission. Basic nutrition laboratory results and zinc levels returned markedly low: 14 μg/dL (reference range, 60–120 μg/dL). Alkaline phosphatase, a zinc-dependent protein, also was low at 12 U/L (reference range, 40–150 U/L). We added trace elements and vitamins and began empiric zinc replacement with 440 mg oral zinc sulfate daily (100 mg elemental zinc). Cephalexin was prescribed for impetiginized skin lesions. The patient noted skin improvement after 3 days on zinc replacement therapy.