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The estimated incidence ranges between 1/3,000-60,000 pregnancies.

Pemphigoid gestationis (PG) typically presents during the second or third trimesters, although onset during the first trimester and postpartum is possible. Pruritus may remain the only symptom. Clinical presentation typically include urticarial papules and annular plaques, erythema multiform-like changes, eczematous lesions, or papulovesicles that in some cases may develop into large tense blisters. Lesions first erupt around the umbilicus and subsequently spread to the abdomen and the extremities. The mucous membranes and the face are typically spared. The clinical course is fairly benign and PG typically resolves with an average duration of 4-6 months. A flare may occur immediately after delivery but typically resolves within 4 weeks. There is an increased risk of small-for-gestational-age baby, premature birth, and development of mild, self-limiting skin lesions in the neonate (10-11% of cases). PG can be associated with the autoimmune Graves disease in the mother.

PG is caused by production of anti-BP180 IgG antibodies that result from antigen presentation by MHC class II molecules aberrantly expressed on amniochorionic stromal cells and on the trophoblast. PG is strongly associated with maternal MHC class II antigens haplotypes HLA-DR3 and HLA-DR4.

Clinical and histological features are not specific to PG; therefore, additional tests are required for diagnosis. Direct immunofluorescence demonstrates a linear deposition of C3 and IgG autoantibodies at the dermal-epidermal junction as in bullous pemphigoid. Indirect immunofluroescence detects serum IgG autoantibodies targeting the basement membrane of the skin in 30%-100% of cases. ELISA (enzyme-linked immunosorbent assay) can reveal circulating IgG antibodies against BP180.

Differential diagnosis includes atopic eruption of pregnancy, polymorphic eruption of pregnancy, and intrahepatic cholestasis of pregnancy, herpes virus infection, urticaria, drug hypersensitivity reactions, contact dermatitis and other eczemas, pityriasis rosea, pityriasis versicolor, yeast folliculitis as well as other types of folliculitis, miliaria, and scabies.

Most patients are controlled with potent or super-potent topical corticosteroids in combination with H1-receptor antagonists such as cetirizine. In more severe cases, oral corticosteroids are necessary. Preferred corticosteroids are prednisone and prednisolone. Minimum effective doses should be used to reduce the risk of side effects, and gradually tapered to a lower maintenance dose. If exacerbation in the peripartum period occurs, the maintenance dose can be increased. Ultraviolet light therapy is relatively contraindicated. In unresponsive cases, patients may benefit from systemic immunoadsorption, or intravenous immunoglobulin. In cases of persisting (postnatal) symptoms, systemic immunosuppressants might be beneficial.

The disease is typically self-limiting; however, onset in the first or second trimester and presence of blisters is associated with adverse pregnancy outcomes. Recurrence in subsequent pregnancies is common (35-50%), and is typically more severe with earlier onset. The disease can persist and converts to bullous pemphigoid (in less than 5% of patients).