A woman with previously undiagnosed common variable immunodeficiency presented with diarrhea and volume depletion. Biopsies from upper and lower endoscopy revealed atrophic gastritis, villous atrophy, and an inflammatory bowel disease-like chronic colitis, with absence of plasma cells in all sites. Cytomegalovirus inclusions were demonstrated in the colon and small bowel mucosa. Despite therapy with intravenous immunoglobulin and ganciclovir, the patient deteriorated rapidly and subsequently died. This case report highlights the potential for cytomegalovirus to cause extensive disease in patients with common variable immunodeficiency and, thus, the importance of considering it in the initial differential diagnosis so that further morbidity and mortality might be prevented.