A rare case of immunotherapy-induced cholangitis and gastritis.

Immune checkpoint inhibitor-related liver injury usually appears as a hepatitis pattern, with a cholangitis pattern being a rare immune-related adverse event. We report a Japanese man in his fifties with immune checkpoint inhibitor-induced cholangitis and gastritis. The patient had been treated for approximately 7 months with carboplatin, pemetrexed sodium hydrate, and bevacizumab for an undifferentiated cancer of unknown primary, with metastases to the right pleura and nasolacrimal duct. The patient was then treated with immune checkpoint inhibitors, including 2 months of atezolizumab followed by 1 month of ramucirumab and docetaxel. Laboratory examinations showed elevated levels of biliary tract enzymes. He complained of generalized fatigue. Computed tomography revealed thickening of the gallbladder and external hepatic bile duct walls and the periportal collar sign. Endoscopic retrograde cholangiopancreatography was negative for bile duct obstruction but showed diffuse asymmetric irregular findings from the hilar region to the distal bile duct. Upper endoscopy showed diffuse irregular erosions and redness. Histopathological examination of specimens of bile duct and gastric mucosa revealed CD8-predominant inflammatory cell infiltrates. We diagnosed the findings as immunotherapy-induced cholangitis and gastritis. Because there are no published reports on immunotherapyinduced cholangitis combined with gastritis, we here report our patient as a rare case.