Primary progressive multifocal leukoencephalopathy presenting as an extrapyramidal syndrome.

We report a 63-year-old woman with a progressive illness which began as a parkinsonian syndrome with bilateral rest tremor, limb rigidity and a gait disorder followed by cognitive decline, visuomotor apraxia and visual agnosia. She died 10 years after the onset of the illness and at autopsy the brain showed characteristic changes of progressive multifocal leukoencephalopathy (PML) with the presence of the JC virus confirmed by in situ hybridisation. Neuropathology also showed some unusual features in the form of atypical linear lesions at the cortico-white matter junction. Some of these lesions were active while others were inactive and similar to the rarely described "burnt out" lesions of PML. PML can in rare cases occur without an underlying immune disorder or malignancy (primary PML) and a parkinsonian syndrome can be produced by a predominantly white matter disorder.