Pembrolizumab-induced pemphigoid nodularis manifesting as an erythema multiforme-like eruption: a case report

Abstract A 56-year-old woman who was being treated with pembrolizumab for a squamous carcinoma of the skin with retroperitoneal metastases developed erythema multiforme-like lesions that progressed to nodular eruptions with erosions and scaling. Histopathological examination of a skin biopsy showed acanthosis, hyperkeratosis, and lymphocytic infiltration. High serum titers of anti-BP180 antibodies (40.96 U/mL; normal < 9.0 U/mL) confirmed pemphigoid nodularis, a rare immune-related adverse event. Treatment with corticosteroids and adjuvant therapies led to complete resolution of the skin lesions while maintaining tumor control, highlighting the importance of early recognition and management of cutaneous immune-related adverse events in patients on immune checkpoint inhibitors.