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Case Reports

Abstract

We report a case of a 62-year-old patient with a 4-month history of painful blistering, initially manifesting as hemorrhagic bullae and erosions on the bilateral medial thighs and dorsal hands. A skin biopsy demonstrated spongiotic dermatitis with neutrophilic microabscesses. Direct immunofluorescence showed linear IgG and C3 deposition at the basement membrane zone, and indirect immunofluorescence on salt-split skin revealed dermal-side binding. Serum IgG autoantibodies to the basement membrane zone were identified on both primate esophagus and primate salt-split skin substrates, with a dermal pattern on the latter. Further immunologic testing revealed positive indirect immunofluorescence for anti-p200 autoantibodies and negative reactivity for laminin 332. The patient failed multiple courses of systemic corticosteroids but responded favorably to dapsone 100 mg daily, with marked clinical improvement. 

Anti-p200 pemphigoid is a rare and likely underrecognized autoimmune subepidermal blistering disorder defined by circulating IgG autoantibodies targeting a 200-kDa dermal protein, most commonly laminin γ1. Clinically, it closely resembles other immunobullous diseases such as bullous pemphigoid and inflammatory epidermolysis bullosa acquisita, presenting with tense bullae, vesicles, erosions, and urticarial plaques. Accurate diagnosis requires a comprehensive approach that integrates histopathology, direct and indirect immunofluorescence, and confirmatory serologic testing. This case highlights the diagnostic challenges posed by anti-p200 pemphigoid, particularly when histopathologic findings are nonspecific. Moreover, it brings attention to the need for increased awareness and broader consideration of this rare entity, while supporting the exploration of alternative treatment strategies beyond corticosteroids in refractory cases, particularly medications that have shown efficacy in other neutrophilic conditions, such as dapsone.