Cytomegalovirus gastritis following immune checkpoint inhibitor-associated gastritis induced by ipilimumab and nivolumab therapy in a patient with renal cell carcinoma

Immune checkpoint inhibitors (ICIs) have been widely used in the treatment of advanced malignancies. By enhancing antitumor immunity through T-cell modulation, ICIs can induce immune-related adverse events (irAEs) resulting from aberrant T-cell activation. We report the case of a 69-year-old woman with renal cell carcinoma and lung metastases who received combination therapy with ipilimumab and nivolumab. After the fifth cycle, she developed anorexia and epigastric pain. Abdominal computed tomography revealed marked thickening of the gastric wall from the antrum to the pylorus, and upper gastrointestinal endoscopy showed erosions with a white coating and thickened gastric folds. Histological examination of a gastric biopsy revealed infiltration of inflammatory cells, and immunohistochemistry demonstrated prominent infiltration of CD8-positive lymphocytes, leading to a diagnosis of irAE gastritis. Treatment with prednisolone was initiated, resulting in improvement of both symptoms and endoscopic findings. However, gastric erosions recurred during tapering of prednisolone. A repeat biopsy showed a reduction in CD8-positive cells but revealed an increase in cytomegalovirus (CMV)-positive cells. Furthermore, serum CMV antigenemia, which was negative before steroid treatment, became positive, supporting the diagnosis of CMV gastritis. Valganciclovir was initiated, and prednisolone was discontinued. Treatment with valganciclovir led to ulcer healing and resolution of CMV antigenemia. Although irAE gastritis is a rare complication of ICI therapy, it should be considered in patients presenting with upper gastrointestinal symptoms during treatment. The management of irAE gastritis requires vigilance for opportunistic infections, timely histopathological evaluation, and careful differentiation from viral infections, especially in cases refractory to corticosteroids.