[A case of Legionnaires' infection with meningeal irritation and abnormal cerebrospinal fluid].

A 60-year-old man was admitted to our hospital because of fever and mental status change. Neurological examination showed meningeal irritation and frontal sign. Cerebrospinal fluid (CSF) examination showed mild pleocytosis and elevated protein. Laboratory findings showed hyponatremia, elevated liver enzymes and creatine phosphokinase, and positive Legionella pneumophila antigen in urine. The chest computed tomographic scans showed consolidation in the left lower lobe lung. We diagnosed Legionnaires' pneumonia and started treatment with levofloxacin. Legionella pneumophila was isolated from culture of the bronchoalveolar lavage fluid, but Legionella culture and polymerase chain reaction in CSF were negative. We hypothesize that Legionella pneumophila could produce nerological symptoms by immune-mediated mechanism associated with elevated IgG index. The neurologist should recognize the presence of the meningo-encephalitis associated with Legionnaires' pneumonia lacking remarkable pulmonary symptoms.