Anti–PD-1-induced bullous pemphigoid in a renal transplant recipient

Immune checkpoint inhibitors, particularly anti-PD-1 agents, are increasingly associated with bullous pemphigoid, a rare yet significant immune-related adverse event. We report a case of immune checkpoint inhibitor-induced bullous pemphigoid in a 74-year-old renal transplant recipient undergoing cemiplimab and later pembrolizumab for recurrent cutaneous squamous cell carcinomas. Bullous pemphigoid developed 23 months after initial immune checkpoint inhibitor exposure and 4 weeks after pembrolizumab reinitiation, presenting with generalized pruritus and tense bullae. Diagnosis was confirmed by histology and direct immunofluorescence. Disease was managed with oral prednisone and topical steroids, with relapses occurring upon tapering. This case highlights the complex interplay between immune checkpoint inhibitors, transplant immunosuppression, and autoimmune toxicity, underscoring the need for personalized, multidisciplinary management strategies in transplant patients receiving immune checkpoint inhibitors.