Similar but different: distinguishing between pemphigus vegetans and pyostomatitis-pyodermatitis vegetans.

A 51-year-old woman presented with a 4-month history of painful ulcers in the mouth and vulva, and painful vegetative plaques at intertriginous sites. Skin biopsies showed squamous hyperplasia and intraepidermal eosinophilic pustulation. Skin direct immunofluorescence (DIF) revealed intercellular deposition of IgG and C3 in the lower part of the epidermis, while serum indirect immunofluorescence (IIF) confirmed the presence of antiepithelial antibodies. The patient was diagnosed with pemphigus vegetans, and successfully treated with dapsone, prednisolone and topical steroids. Although pemphigus vegetans and pyostomatitis-pyodermatitis vegetans can show identical clinical and histological features, the presence or absence of comorbid inflammatory bowel disease, and the results of both skin DIF and serum IIF can be used to distinguish between these two conditions. This case report explores the challenges in making this distinction, and the implications of establishing the correct diagnosis.