This antigen, which is a minute fraction of the total amount of proteins extracted, has been further characterized on polyacrylamide gel electrophoresis as two closely spaced proteins whose molecular weight is in the 220 to 240 kd range. A study that used extracts of cultured human epidermis confirmed that a constituent of the basement membrane, a 230 kd polypeptide, is the major bullous pemphigoid antigen. In this study, sera from 36 of 37 patients with bullous pemphigoid showed antibodies to this protein. The bullae vary in size and shape and may appear on normal skin or erythematous, pruritic skin. Bullae may be generalized or localized to the trunk or the extremities.
Oral involvement is uncommon.
Nikolsky's sign is absent. The histologic picture shows subepidermal bullae caused by detachment of the epidermis from the dermis. A dermal infiltrate of neutrophils and some mononuclear cells is present in inflamed lesions. The differential diagnosis of bullous pemphigoid includes other autoimmune disorders that resemble this blistering disease, such as cicatricial pemphigoid, herpes gestationis, dermatitis herpetiformis, and epidermolysis bullosa acquisita. The eruption may be controlled by oral prednisone, administered initially in a daily dose of 60 to 100 mg.