Fatal Toxic Megacolon Following Nivolumab and Ipilimumab Therapy in Metastatic Melanoma: A Case Report.

In this case report, we describe a 76-year-old man with advanced malignant melanoma who developed severe colitis and toxic megacolon following nivolumab plus ipilimumab therapy. Despite treatment with prednisolone, infliximab, and vedolizumab, the patient's condition deteriorated, resulting in hypoalbuminemia and unfeasibility of surgical intervention. Elevated C-reactive protein (CRP) levels served as a critical diagnostic clue, prompting abdominal radiography, which subsequently confirmed the diagnosis of toxic megacolon. This case highlights a rare but life-threatening complication of immune checkpoint inhibitors and underscores the challenges in managing refractory immune-related colitis. Given the increasing use of immune checkpoint inhibitors in clinical practice, this report will be of significant interest to readers by emphasizing the importance of timely recognition, CRP monitoring, and intervention to prevent fatal outcomes in similar cases.