Progressive Multifocal Leukoencephalopathy PML

The disease is associated with the JC virus (named after the initials of the patient in whose brain the virus was first detected) and the SV40 virus, both papovaviruses. The disease commonly develops in immunocompro-mised adults and in patients with leukemias, lymphomas, and transplanted organs. Patients with AIDS are at high risk.

The onset of PML is insidious. The patient presents with behavioral changes, progressive cognitive decline and a variety of neurologic symptoms and signs. The clinical course is usually several months. CT scan demonstrates hypodense and MRI T2-weighted images hyperintense, usually nonenhancing multiple lesions, predominantly in the subcortical white matter, brain-stem and cerebellum.

Grossly, multiple, ill-defined, soft, slightly granular areas are dispersed in the white matter of the cerebral hemispheres, brainstem, and cerebellum.

Histological features include (a) multiple confluent demyelinations with relative sparing of the axons (Fig. 6.19); (b) the presence of giant, bizarrely shaped, often multinucleated astrocytes and swollen oli-godendrocytes in the demyelinated areas; (c) eosino-philic intranuclear viral inclusions in oligodendrocytes and astrocytes; and (d) perivascular lymphocytic infiltrations.

FIGURE 6.19

Progressive multifocal leukoencephalopathy. Multifocal myelin losses in subcortical white matter (myelin stain).

FIGURE 6.19

Progressive multifocal leukoencephalopathy. Multifocal myelin losses in subcortical white matter (myelin stain).

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