A case of coexisting brain abscess and cytomegalovirus encephalitis during chemoradiotherapy for breast cancer

A 67-year-old woman undergoing chemoradiotherapy for breast cancer had fever and impaired consciousness. Brain MRI showed abnormal signals in the bilateral frontal lobes. The patient was diagnosed with a brain abscess. The abnormal signal in the right frontal lobe decreased in size with antibiotic treatment, but the abnormal signal in the left frontal lobe worsened. Cytomegalovirus (CMV) was detected in the cerebrospinal fluid. Following administration of ganciclovir, the abnormal signal in the left frontal lobe decreased in size and consciousness improved. Based on the clinical course, we diagnosed a coexisting brain abscess and CMV encephalitis. However, the patient died of respiratory failure caused due to progression of breast cancer and underwent an autopsy. Pathological findings suggested different etiologies for the left and right frontal lobes. They supported the clinical diagnosis of coexisting brain abscess and cytomegalovirus encephalitis. This case indicated that in immunosuppressed patients, coexisting CMV infection and bacterial infection should be considered.