Snapshot A 29-year-old G1P0 woman at 30 weeks pregnancy presents to her dermatologist for a rash that started on her abdomen. She reports having significant itch with this rash. She denies any new cosmetic or medication exposures in the past few months. Her pregnancy is otherwise healthy, without complications. On physical exam, she has multiple edematous pink papules and plaques on her abdomen without scale. There is one tense intact bulla noted on the left lower abdomen. A biopsy is done and sent for histology and direct immunofluorescence, which shows a subepidermal split. Introduction Overview pemphigoid gestationis, also known as herpes gestationis, is an autoimmune bullous dermatosis that occurs during the second or third trimester of pregnancy, or in the immediate postpartum period treatment is usually oral corticosteroids Associated conditions thyroid disease, particularly Graves disease premature birth Epidemiology Incidence 1 in 50,000 pregnancies Demographics pregnant women Risk factors associated with HLA-DR3 and HLA-DR4 history of pemphigoid gestationis with previous pregnancies ETIOLOGY Pathogenesis mechanism antibody to BPAG2, a component of the hemidesmosome BPAG2 is also known as BP180 it is unclear why antibodies form hypotheses include cross-reactivity between placental tissue and the skin Presentation Symptoms periumbilical rash that progresses to tense bullae significant pruritus flares with delivery of neonate Physical exam inspection edematous pink urticaria-like papules and plaques tense vesicles or bulla spares mucous membranes Studies Histology dermal edema subepidermal bullae eosinophils Direct immunofluorescence (DIF) linear C3 (some with IgG) deposition at the basement membrane Differential Polymorphic eruption of pregnancy key distinguishing factors may also present with pruritic urticarial papules and plaques on the abdomen, but will not progress to bullae DIF is negative Treatment Medical oral corticosteroids indications symptomatic relief typically, topical corticosteroids are not effective Complications Fetal risk increased risk of premature birth Prognosis Good May resolve spontaneously after delivery