A Case of Severe Immune Checkpoint Inhibitor-associated Gastritis Treated with Steroids and Infliximab

This case report describes a 77-year-old man with severe immune-related gastritis after receiving pembrolizumab for lung cancer. Despite initial steroid therapy, he showed no improvement and was diagnosed with steroid refractory immune-related gastritis. Infliximab was added to steroid therapy, resulting in significant clinical and endoscopic improvement. This highlights the importance of early diagnosis of immune-related gastritis by endoscopic and histological findings. Prompt evaluation of steroid efficacy and the early use of infliximab in steroid refractory cases are emphasized for effective management of immune-related gastritis as the indications for immune checkpoint inhibitors have expanded.