2025 Volume 67 Issue 7 Pages 1279-1285
A 78-year-old man experienced mucous and bloody stools for several months, which worsened after a second pembrolizumab administration for right middle lobe lung cancer. CS revealed erythematous and edematous mucosa throughout the colon, and biopsy revealed apoptosis. Therefore, the patient was diagnosed with immune-related enteritis, and prednisolone therapy was initiated. As the symptoms did not improve, endoscopy was reperformed, which revealed worsening inflammation of the entire colon and multiple rectal ulcerations. Histopathologically, apoptosis had disappeared, and the patient may have developed ulcerative colitis before pembrolizumab administration. Subsequently, the patient was treated with vedolizumab and improved rapidly. If inflammatory bowel disease symptoms are suspected, CS should be considered before initiating treatment with immune checkpoint inhibitors.
