Bullous pemphigoid associated with cemiplimab therapy in a patient with locally advanced cutaneous squamous cell carcinoma

Cemiplimab (Libtayo, Regeneron Pharmaceuticals, Tarrytown, NY) is a monoclonal antibody that targets the programmed cell death receptor 1. In 2018, the Food and Drug Administration approved cemiplimab for the treatment of patients with metastatic cutaneous squamous cell carcinoma (SCC) or locally advanced cutaneous SCC that is not a candidate for surgery or radiation.1 Immune checkpoint inhibitors have been implicated in the development of bullous disorders.2,3 We report the first case, to our knowledge, of a patient who developed severe steroid-resistant bullous pemphigoid shortly after initiating therapy with cemiplimab, requiring discontinuation of the programmed cell death receptor 1 inhibitor and treatment with rituximab.