Pustular psoriasis of pregnancy (PPP) is a rare but potentially serious dermatosis of pregnancy. Left untreated, PPP can be fatal for both the mother and the fetus.1,2 Contrary to many other pregnancy dermatoses, which are typically limited to the skin, systemic signs and symptoms often accompany PPP, including fatigue, fever, diarrhea, delirium, elevated markers of inflammation such as an increased erythrocyte sedimentation rate, and increased white blood cell counts.1,3,4 Progression of the rash to erythroderma with subsequent dangerous fluid and electrolyte imbalances, loss of thermoregulation in the skin, and the risk for secondary infection and sepsis can occur in severe cases.1,5
Increasing evidence suggests that PPP is likely a variant of generalized pustular psoriasis (GPP), which can be vulnerable to a variety of triggers, including metabolic disturbances, systemic steroid withdrawals, and pregnancy; however, classification of the disease as either a variant of disease or a distinct disease state remains controversial.1,6 Early recognition and prompt treatment are critically important given the potential for fetal and maternal morbidity and mortality that is associated with PPP.1,6,7
Most cases of PPP involve presentation in the early part of the third trimester of pregnancy; postpartum PPP has been reported but is exceedingly rare.1 Typically, lesions develop in the skin folds and spread centrifugally.2,6 The lesions usually begin as erythematous plaques with a pustular ring with a central erosion. The face, palms, and soles of the feet usually are spared; occasionally, involvement of oral and esophageal mucosae is seen. Biopsy findings usually comprise spongiform pustules with neutrophil invasion into the epidermis. Characteristic laboratory findings include electrolyte derangements with elevated erythrocyte sedimentation rate and leukocytosis.2,8
As was seen in the case presentation, PPP largely resolves following childbirth; however, there is a significant risk for recurrence in subsequent pregnancies, which may be more severe and present earlier.1,6 Menstrual cycle changes and the use of oral contraceptives, particularly those containing progesterone, also have been associated with PPP flares.1,6 Although its pathophysiology is not entirely understood, the development of PPP is believed to be associated with the hormonal changes that occur in the third trimester, in particular elevated progesterone levels.6
Oral corticosteroids remain the mainstay of treatment for PPP.6 Lower dosages ranging from 15 to 30 mg daily can be used for mild cases.1 More severe cases usually are treated with an initial trial of prednisone or prednisolone with dosages ranging from 30 mg daily to as high as 60 to 80 mg daily. Higher doses should be used with caution, however, as they may result in reduced fetal reactivity on fetal monitoring.1,9 Treatment at least throughout the remainder of a patient’s pregnancy usually is required, with subsequent gradual tapering of the medication.1
Although it was once reserved for severe or refractory PPP, in 2012, a task force from the National Psoriasis Foundation categorized cyclosporine as an appropriate first-line therapy for PPP.10 Published case reports have documented the successful treatment of PPP with cyclosporine in cases that did not respond to systemic steroids.6,11
Several case reports have documented the safe use of anti–tumor necrosis factors (TNFs), primarily infliximab, for PPP.12 Infliximab and other TNF-α antibodies are pregnancy category B, but limited controlled human data exist regarding their safety in pregnancy.1
Finally, the addition of narrowband UVB light therapy to oral corticosteroids also has been proposed as a safe treatment of refractory disease.6,13 Unlike psoralen plus UVA, which is usually reserved for postpartum use, narrowband UVB light therapy has been shown to be safe for use during pregnancy.1
Genetic and pathogenesis studies have described involvement of IL-1 and IL-36 cytokines in GPP.1 These interleukins are important in neutrophil chemotaxis leading to pustule formation. In addition, as in other psoriasis variants, TNF-α and IL-17α are important. Such findings may help to pave the way for the development of future therapies for both GPP and PPP.
Clinicians should have a high index of suspicion for PPP in pregnant women who present with widespread cutaneous eruptions. Presently, oral corticosteroids paired with close involvement of obstetric care remains the cornerstone of treatment for PPP. As the case report illustrates, effective diagnosis, treatment, and monitoring are essential for safe outcomes for both mother and baby.