Usefulness of immunofluorescence overlay antigen mapping in the identification of autoantigen in anti‐p200 pemphigoid

Abstract

AbstractAnti‐p200 pemphigoid is a rare subepidermal blistering disease showing immunoglobulin G (IgG) autoantibodies reactive with a 200‐kDa protein. In most patients, serum IgG antibodies react with laminin γ1. The diagnosis of anti‐p200 pemphigoid is occasionally difficult, mainly due to the lack of standardized tests. We performed fluorescence overlay antigen mapping by laser scanning confocal microscopy (FOAM‐LSCM) to identify autoantigens in an anti‐p200 pemphigoid patient and assessed its usefulness for the diagnosis. A 71‐year‐old man presented with blisters and erosions on the bilateral forearms. No mucosal lesions were observed. Laboratory examinations revealed mild leukocytosis and antinuclear antibody negativity. A histopathological examination showed subepidermal blisters with neutrophil infiltration. Direct immunofluorescence showed linear IgG staining along the basement membrane zone. Indirect immunofluorescence using 1 M NaCl‐split skin sections revealed IgG reactivity on the dermal side. Immunoblotting detected circulating IgG autoantibodies that reacted with a 200‐kDa protein. Accordingly, anti‐p200 pemphigoid was diagnosed. FOAM‐LSCM revealed that the patient's IgG signals were co‐localized with laminin γ1 but were observed above type VII collagens. A direct immunofluorescent analysis for IgG deposition patterns showed an n‐serrated pattern. Thus, FOAM‐LSCM may be useful for diagnosing anti‐p200 pemphigoid.