Abstract A 17-year-old woman who was being treated with prednisolone for cutaneous vasculitis developed recurrent massive melena and abdominal pain. An emergency resection was performed because of uncontrollable melena, revealing many small intestinal ulcers with cytomegalic inclusion bodies, which were found by immunopathological staining. However, the cytomegalovirus (CMV) antigenemia (CMV-Ag) assay and the IgM antibody titer for CMV were negative on admission. This case indicates that a high state of alertness for CMV infection in immunocompromised patients with gastrointestinal bleeding is required even if the CMV-Ag assay and IgM antibody are both negative.