A Case of Pemrolizumab-Associated Severe Gastritis Treated with Mycophenolate Mofetil

Immune checkpoint inhibitors have become a frequently used treatment in oncology practice. Although it has approved indications in many types of cancer, phase studies are ongoing in many types of cancer. Side effects due to the increasing use of immune checkpoint inhibitors have begun to be seen frequently. Cases of colitis, pancreatitis and hepatitis due to immune check point inhibitors have been reported very frequently; However, the number of gastritis cases is limited. Here, we presented a case of severe gastritis due to pembrolizumab in a patient with cholangiocellular carcinoma. When side effects develop due to immune check point inhibitors, infliximab and mycophenolate mofetil (MMF) treatments are used in steroid-refractory patients. In our patient, MMF treatment was started due to possible infectious processes due to a recent attack of cholangitis and the inability to remove the stones in the common bile duct. Response to MMF treatment was obtained after 3 months. We would like to state that MMF treatment is an option in cases that develop due to immune check point inhibitors. MMF treatment was used in a case of severe gastritis due to pembrolizumab, as it did not respond to steroid treatments. The patient responded after MMF treatment. We planned to present this rare side effect of pembrolizumab and the treatment strategies we applied in the development of side effects.