Pemphigoid nodularis associated with autoantibodies to the NC16A domain of BP180 and a hyperproliferative integrin profile

Pemphigoid nodularis, a rare variant of bullous pemphigoid, has clinical features resembling prurigo nodularis, with blisters arising from normal-appearing or nodular skin. The fine antigenic epitope of the autoantibodies and the mechanism accounting for the nodular phenotype has not been delineated. We describe a patient with pemphigoid nodularis that fulfilled the criteria of bullous pemphigoid by histopathologic examination and direct and indirect immunofluorescence studies. Immunopathologic examination also revealed in situ deposition and circulating autoantibodies of all IgG subclasses, except IgG3, and both light chains to the patient's skin basement membrane. By immunoblotting, the patient's IgG autoantibodies labeled BP180, BP230, and an unidentified 150-kd epidermal protein and mapped the BP180 epitope to the MCW-1, region 2 of the NC16A domain. The nodular plaque skin showed expression of α-6 and β-1 integrin subunits, mediators of matrix-cell signaling and proliferation, at the basal and the suprabasal epidermis, a pattern found in psoriasis, which is the prototype of hyperproliferative dermatoses.