Checkpoint Inhibitor–Induced Colitis: A New Type of Inflammatory Bowel Disease?

Checkpoint inhibitors are immune-stimulatory antibodies that have transformed the management and prognosis of individuals with metastatic melanoma and other cancers. Checkpoint inhibitor–induced colitis is an increasingly recognized immune-related adverse event that shares many of the same phenotypical, serological, and histological characteristics of both Crohn’s disease and ulcerative colitis, suggesting that checkpoint inhibitor–induced colitis may represent a new inflammatory bowel disease phenotype. We report a 73-year-old man with metastatic melanoma who developed ipilimumab-induced colitis with subsequent transformation to Crohn?s colitis-like phenotype after the addition of pembrolizumab.