Pustular psoriasis of pregnancy (PPP), also known as impetigo herpetiformis, is a relatively rare cutaneous disorder of pregnancy wherein lesions typically appear in the third trimester and resolve after delivery; however, lesions may persist through the postpartum period. Pustular psoriasis of pregnancy may be considered a fifth dermatosis of pregnancy, alongside the classic dermatoses of atopic eruption of pregnancy, intrahepatic cholestasis of pregnancy, pemphigoid gestationis, and pruritic urticarial papules and plaques of pregnancy.1
As PPP is a rare disease, its effects on maternal-fetal health outcomes and management remain to be elucidated. Though maternal mortality is rare in PPP, it is a unique dermatosis of pregnancy because it may be associated with severe systemic maternal symptoms.2 Fetal morbidity and mortality are less predictable in PPP, with reported cases of stillbirth, fetal anomalies, and neonatal death thought to be due largely to placental insufficiency, even with control of symptoms.1,3 Given the risk of serious harm to the fetus, reporting of cases and discussion of PPP management is critical.
Case Report
An otherwise healthy 29-year-old G2P1 woman at 32 weeks’ gestation presented to our emergency department with a 1-week history of a pruritic, burning rash that started on the thighs then spread diffusely. She denied any similar rash in her prior pregnancy. She was not currently taking any medications except for prenatal vitamins and denied any systemic symptoms. The patient’s obstetrician initiated treatment with methylprednisolone 50 mg once daily for the rash 3 days prior to the current presentation, which had not seemed to help. On physical examination, edematous pink plaques studded with 1- to 2-mm collarettes of scaling and sparse 1-mm pustules involving the arms, chest, abdomen, back, groin, buttocks, and legs were noted. The plaques on the back and inner thighs had a peripheral rim of desquamative scaling. There were pink macules on the palms, and superficial desquamation was noted on the lips. The oral mucosa was otherwise spared (Figure 1).
Figure 1. Pink plaques with rare pustules coalescing on the abdomen in pustular psoriasis of pregnancy.
Biopsy specimens from the left arm revealed discrete subcorneal pustules with mild acanthosis of the epidermis with spongiosis (Figure 2). The papillary dermis showed a sparse infiltrate of neutrophils with many marginated neutrophils within vessels. Direct immunofluorescence was negative for human IgG, IgA, IgM, complement component 3, and fibrinogen. Laboratory workup revealed leukocytosis of 21.5×109/L (reference range, 4.5–11.0×109/L) with neutrophilic predominance of 73.6% (reference range, 56%), an elevated erythrocyte sedimentation rate (ESR) of 40 mm/h (reference range, 0–20 mm/h), and a mild hypocalcemia of 8.6 mg/dL (reference range, 8.2–10.2 mg/dL). The patient was started on methylprednisone 40 mg once daily with a plan to taper the dose by 8 mg every 5 days.
Figure 2. A biopsy of a lesion on the left arm in a patient with pustular psoriasis of pregnancy revealed discrete subcorneal pustules. The papillary dermis showed mild edema and a sparse infiltrate of neutrophils and eosinophils (H&E, original magnification ×100).
At 35 weeks’ gestation, the patient continued to report pruritus and burning in the areas where the rash had developed. The morphology of the rash had changed considerably, as she now had prominent, annular, pink plaques with central clearing, trailing scaling, and a border of subtle pustules on the legs. There also were rings of desquamative scaling on the palms. During follow-up at 37 weeks’ gestation, the back, chest, and abdomen were improved from the initial presentation, and annular pink plaques with central clearing were noted on the legs (Figure 3). Given the clinical and histopathologic findings, a diagnosis of PPP was made. It was recommended that she undergo increased fetal surveillance with close obstetric follow-up. Weekly office visits with obstetrics and twice-weekly Doppler ultrasounds and fetal nonstress tests were deemed appropriate management. The patient was scheduled for induction at 39 weeks’ gestation given the risk for potential harm to the fetus. She was maintained on low-dose methylprednisolone 4 mg once daily for the duration of the pregnancy. The patient continued to have gradual improvement of the rash at the low treatment dose.
Figure 3. During follow-up at 37 weeks’ gestation, improvement was noted in a patient with pustular psoriasis of pregnancy following a 40-mg methylprednisolone taper. Annular pink plaques with central clearing were noted on the legs.
Following induction at 39 weeks’ gestation, the patient vaginally delivered a healthy, 6-lb male neonate at an outside hospital. She reported that the burning sensation improved within hours of delivery, and systemic steroids were stopped after delivery. At a follow-up visit 3 weeks postpartum, considerable improvement of the rash was noted with no evidence of pustules. Fading pink patches with a superficial scaling were noted on the back, chest, abdomen, arms, legs (Figure 4), and fingertips. The patient was counseled that PPP could recur in subsequent pregnancies and that she should be aware of the potential risks to the fetus.
Figure 4. At a follow-up visit 3 weeks postpartum, considerable improvement of the rash from pustular psoriasis of pregnancy was noted on the legs.