Acute gastritis caused by concurrent infection with Epstein–Barr virus and cytomegalovirus in an immunocompetent adult

Herein, we describe an extremely rare case of gastritis due to concurrent infection with Epstein–Barr virus (EBV) and cytomegalovirus (CMV) occurring in an immunocompetent adult. The patient was a 35-year-old man who presented with slight fever, nausea, anorexia, weight loss for 3 weeks, mild transaminitis, and leukocytosis with atypical lymphocytes in peripheral blood. The clinical presentation and elevated IgM titers to both EBV-VCA and CMV strongly suggested infectious mononucleosis syndrome caused by co-infection with EBV and CMV. A computed tomographic scan of the abdomen showed diffuse thickening of the gastric wall mimicking linitis plastica, and upper endoscopy revealed thickened and eroded mucosa throughout the stomach. Histologic examination of gastric biopsies showed a dense lymphoid and neutrophilic infiltrate in the lamina propria with erosion. In situ hybridization assay revealed many lymphocytes positive for EBV-encoded RNA. Moreover, immunohistochemistry using an anti-CMV monoclonal antibody identified some CMV-positive cells (i.e. foveolar epithelium and endothelium). We finally diagnosed this case as gastric involvement in infectious mononucleosis, and the patient recovered without the administration of antiviral drugs. To our knowledge, this is the first reported case of gastritis co-infected with EBV and CMV, as a manifestation of infectious mononucleosis in an immunocompetent adult.