Anti-p200 pemphigoid: a novel autoimmune subepidermal blistering disease.

Anti-p200 pemphigoid is a recently defined autoimmune subepidermal blistering disease characterized by circulating and tissue-bound autoantibodies to a 200-kDa protein (p200) of the dermal-epidermal junction (DEJ). This DEJ constituent is thought to be important for adhesion of basal keratinocytes to the underlying dermis. While the exact identity of p200 remains unknown, it has been demonstrated to be immunologically and biochemically distinct from all major autoantigens of the DEJ, including bullous pemphigoid antigens 180 and 230, laminin 1, 5 and 6, alpha6beta4 integrin, and type VII collagen. Clinically, most reported cases present with tense blisters as well as urticarial papules and plaques, closely resembling bullous pemphigoid. Histopathological examination of lesional skin biopsies shows subepidermal split formation and superficial inflammatory infiltrate typically dominated by neutrophils. Immunopathologically, linear deposits of immunoglobulin (Ig)G and C3 are detected along the DEJ by direct immunofluorescence microscopy of perilesional skin. Indirect immunofluorescence microscopy of patients' sera on NaCl-split human skin demonstrates circulating IgG autoantibodies labeling the dermal side of the split. By immunoblotting, these autoantibodies recognize a 200-kDa protein of human dermis. Biochemical characterization of the p200 molecule revealed a noncollagenous N-glycosylated acidic protein with an isoelectric point of approximately 5.5. We present an overview of the pathogenesis, clinical features, diagnosis and treatment of this new disease entity.