A rare presentation of pemphigus vegetans as an isolated vegetative lesion - review of histopathological clues and treatment effects in multiple biopsies.

Pemphigus is a group of immunobullous dermatoses characterized by the presence of autoantibodies directed against adhesion molecules of keratinocytes, with pemphigus vegetans being the rarest form, accounting for 1-2% of all cases of pemphigus. Pemphigus vegetans is featured by verrucous vegetative lesions in addition to vesiculobullous lesions. We report a rare case of pemphigus vegetans presenting as an isolated vegetative lesion in the groin three months prior to the development of blisters. Owing to the atypical presentation, multiple biopsies were performed before and after corticosteroid treatment. Comparing the histopathology of pre- and post-treatment biopsies, the resolution of intraepidermal microabscesses, and reduction in intraepidermal and dermal inflammatory infiltrates, spongiosis and interface change, favorably attributable to treatment, were noted. However, direct immunofluorescence showed persistent intracellular intraepidermal deposition of IgG and C3 two weeks into treatment, despite near complete resolution of blisters on clinical examination. Clinical regression of the vegetative lesion was noted only after 6 weeks into corticosteroid treatment, while histopathological evidence of treatment was apparent at the second week. The current case illustrates the importance of a liberal use of immunofluorescence studies in establishing the uncommon yet significant diagnosis of pemphigus vegetans, particularly for vegetative lesions that are persistent, in the intertriginous areas and/or in the presence of concurrent cutaneous or mucosal symptoms. This article is protected by copyright. All rights reserved.