Bullous pemphigoid in a patient with psoriasis and possible drug reaction: a case report.

Bullous pemphigoid, first described in 1953 by Lever, is the most common autoimmune blistering skin disease. As such,this disorder may be encountered relatively frequently in the dermatologist's office, though it is a rarity on the inpatient medicine wards. Lesions develop when autoantibodies are directed against glycoproteins BPAG1 and BPAG2, hemidesmosomes that are embedded in the epidermal basement membrane. The immune complex triggers a complement cascade that activates neutrophils and eosinophils, resulting in the release of proteolytic enzymes. As a result, subepidermal bullae develop; the diagnosis is confirmed by histological examination of skin biopsy. The case of bullous pemphigoid described here presented the treating team with some diagnostic challenges because of the patient's concomitant history of psoriasis and apparent dermatologic reaction to cephalexin. Though the patient's skin lesions resolved rapidly with appropriate treatment, the case generated many questions about the diagnosis and most effective management of bullous pemphigoid.