Brain stem and cerebellar dysfunction with Legionnaires' disease.

A 37-year-old man under treatment for manic-depressive illness developed pneumonia identified as Legionnaires' disease accompanied by a severe neurological disorder with profound dysarthria, ataxia, gaze paralysis, and downbeat nystagmus. At review six months later, he has made only a partial recovery with persisting limb and gait ataxia. Difficulties in diagnosing neurological complications of Legionnaires' disease in a patient with a psychiatric disorder requiring psychotropic medication are discussed.