Progressive multifocal leukoencephalopathy: clinical description and demonstration of the causal agent.

A 40 year old man with AIDS had memory deficit and visual impairment. The brain magnetic resonance images showed abnormalities in the white matter not enhanced with gadolinium. JC-virus DNA was detected in the cerebrospinal fluid. He died after a few weeks of progressive neurologic deterioration. Histologic examination showed changes compatible with progressive multifocal leukoencephalopathy. Polyoma virus etiology was confirmed by immunostaining of brain tissue sections and electron microscopy of infected oligodendrocytes.