Drug-induced bullous pemphigoid with dermal fluorescence on salt-split skin

Abstract

The immunological features of drug-induced bullous pemphigoid appear to be similar to those of idiopathic bullous pemphigoid (BP), with presence of circulating and tissue-bound antibodies showing anti-basement membrane zone specificity. We describe a 28-year-old woman who developed a widespread blistering eruption with marked involvement of the mucous membranes shortly after commencing treatment with oral flucloxacillin. The eruption gradually cleared following drug withdrawal and treatment with oral corticosteroids. Indirect immunofluorescence showed circulating IgG anti-basement membrane zone (BMZ) antibody and C3 which bound to the dermal aspect of salt-split skin, and direct immunofluorescence (IMF) of perilesional skin showed a linear band of C3 at the BMZ. Western immunoblotting of the patient's serum showed positive reactivity with a 180 kDa antigen in epidermal extracts and no reactivity with dermal extracts. The dermal-binding pattern on indirect IMF with salt-split skin only occurs in a minority of patients with BP and has not been described previously in a drug-induced case.