A Case of Fulminant Immune‐Related Enterocolitis During Immune Checkpoint Inhibitor Therapy for Metastatic Renal Cell Carcinoma

Introduction: Combination therapy with immune checkpoint inhibitors (ICIs) has become a standard treatment for metastatic renal cell carcinoma (mRCC). However, ICIs may also cause immune-related adverse events. We report a case of mRCC that developed fulminant immune-related enterocolitis. Case Presentation: A 79-year-old man received ICIs therapy for mRCC and was urgently hospitalized because of worsening diarrhea. Despite the initiation of steroid therapy, circumferential intestinal necrosis developed, necessitating subtotal colectomy. The patient subsequently developed cytomegalovirus- and Epstein-Barr virus-associated enterocolitis and died from extensive intestinal necrosis caused by severe thrombosis secondary to disseminated intravascular coagulation. Conclusion: Persistent diarrhea during ICIs therapy requires prompt evaluation and specialist consultation, even when symptoms appear mild, as they may signal immune-related enterocolitis. Clinicians should also remain vigilant for infectious complications, which can exacerbate the severity of immune-related enterocolitis and lead to life-threatening outcomes.