[Case of paraneoplastic limbic encephalitis associated with malignant B cell lymphoma].

We report a case of a 62-year-old man with limbic encephalitis associated with diffuse large B cell lymphoma. He was hospitalized for the assessment of cognitive disturbance and changes in characteristics. Neurological examination revealed disturbance of recall and recent memory. Magnetic resonance (MR) imaging of the brain revealed bilateral atrophy of the medial temporal lobes. Cerebrospinal fluid (CSF) examination revealed mononuclear pleocytosis and elevated protein levels. Herpes simplex virus DNA was not detected in the CSF by the polymerase chain reaction. Immunological investigation of the patient's serum samples showed no evidence of acute infection with herpes simplex virus or cytomegalovirus. Chest computed tomography (CT) revealed a mass lesion on the right hilum of the lung. Therefore, tumor resection was performed. The pathological diagnosis was diffuse large B cell lymphoma. We diagnosed this patient with paraneoplastic limbic encephalitis. Chemotherapy was performed, but the patient's clinical symptoms failed to improve. We investigated 7 previously reported cases of paraneoplastic limbic encephalitis associated with malignant lymphoma in Japan. We suggest that an early diagnosis of paraneoplastic limbic encephalitis with progressive symptoms such as changes in characteristics is important. Early diagnosis and treatment of malignant tumors is desirable to facilitate clinical recovery and improve prognosis.