H. PROGRESSIVE MULTIFOCAL LEUKOENCEPHALOPATHY (PML)

1. Clinical features

a. Onset: occurs in patients with associated immune suppression or chronic disease, e.g. lymphoma, AIDS

b. Clinical presentation: The major consistent symptom is intellectual deterioration and dementia. Other symptoms include cortical visual symptoms, motor disorders, abnormal movements (e.g. chorea).

c. Duration: death usually in 2-6 months

d. CSF findings: normal

2. Pathological changes

a. Gross pathology: Demyelination with resulting ventricular dilatation

b. Microscopic pathology: Inclusion bodies in oligodendroglia nuclei; transformed bizarre astrocytes and gliosis; numerous areas of demyelination (due to oligodendrocyte dysfunction). Lesions are primarily in subcortical white matter, but also occur in brainstem and cerebellum. Ultrastructural changes include identification of papovavirus particles in the oligodendroglial nuclear inclusions.

This high power microscopic view shows giant bizarre astrocytes in a case of progressive multifocal leukoencephalopathy.

This image shows oligodendrocyte nuclear inclusions in a case of progressive multifocal leukoencephalopathy.

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