[Progressive multifocal leukoencephalopathy. Demyelinating viral disease--common complication of AIDS].

PML is a chronic, progressive, fatal disease in the CNS of humans. Characteristic pathologic features are spotty demyelination, enlarged oligodendrocytes with nuclear inclusions, and transformed astrocytes. It is caused by the polyoma virus JCV, which has worldwide distribution and usually is harmless. In some individuals with impaired cell-mediated immunity, most commonly in aids, virus changes into a pathogenic form. Hence, PML is a slow, viral, opportunistic infection. The infection is productive in astrocytes and destructive in oligodendrocytes. Lysis of the latter causes demyelination. The discovery of PML in 1958 opened the door to extensive research in several fields of biomedicine.