Pembrolizumab-induced bullous pemphigoid

Background: Bullous pemphigoid (BP) is an autoimmune blistering disorder characterized by autoantibody deposition at the epithelial basement membrane zone. It classically presents in elderly adults and can be idiopathic or drug-induced. The 2 major bullous pemphigoid antigens do not differ between the drug-induced and idiopathic variants of the disease, nor do the direct and indirect immunofluorescence (DIF and IIF) findings. Pembrolizumab is an anti–programmed cell death 1 (PD-1) antibody which inhibits the negative immune regulation caused by PD-1 receptor signaling resulting in reversal of T-cell suppression and induction of antitumor responses.