A rare case of Pseudomonas aeruginosa enteritis induced by pembrolizumab.

A 72-year-old male had pseudomonal enteritis related to pembrolizumab. Chemotherapy for hypopharyngeal carcinoma with lung metastasis comprised cisplatin, 5-FU, and pembrolizumab. On day 14 of chemotherapy treatment he had a sudden prominent abdominal bulge, decreased consciousness, and drop in blood pressure in septic shock. CT scan showed marked intestinal gas through to intrahepatic bile ducts. Pseudomonas aeruginosa was simultaneously detected in both blood and stool cultures. Intestinal endoscopy revealed ulcerative lesions from the transverse colon to the rectum. Pathological investigations indicated apoptosis of the villus. The patient was diagnosed with pseudomonal enteritis induced by immune-related adverse events from the use of pembrolizumab. Treatment by corticosteroid and meropenem were subsequently switched to cefepime and metronidazole, and this successfully improved his colitis. In this new era of biological-targeted drugs and as clinical experience grows, we recommend a high level of alertness for potential diagnosis of infectious complications.