Bullous pemphigoid in a patient treated with UVA-1 phototherapy for disseminated morphea

Bullous pemphigoid is an autoimmune disease of the skin characterized by the production of antibodies directed at structures of the basement membrane zone (BMZ) leading to subepidermal blisters. Several causative triggers have been described in the literature, among them UV light. Here, we report on a 73-year-old Caucasian female with disseminated morphea who developed blisters on her extremities after receiving whole-body UVA-1 phototherapy. The initial differential diagnosis of a phototoxic versus photoallergic reaction was ruled out as the lesions continued to spread after discontinuation of phototherapy. Histological and direct immunofluorescence examination showing a subepidermal blister and linear IgG deposits along the BMZ along with detection of circulating anti-BMZ antibodies led to the diagnosis of bullous pemphigoid. Immunosuppressive therapy resulted in regression of all blisters. After ruling out other possible causes, such as neoplasias or drugs, we conclude that UVA-1 has to be regarded as the most likely trigger of the disease.