Pathomorphological variations of the AIDS-associated progressive multifocal leukoencephalopathy.

Pathological analysis of 20 cases of the progressive multifocal leukoencephalopathy (PML) appearing in the course of acquired immune deficiency syndrome (AIDS) is presented. PML occurred in 10% of all AIDS cases, collected in the period from 1987 to 1999. PML appeared either as the only brain pathology or accompanied HIV-related brain alterations isolated or concomitant with one or several opportunistic infections and/or neoplastic growth (malignant lymphoma). Basing on the pathomorphological picture and clinical symptomatology early, atypical and severe forms of the disease were distinguished. All of them were characterized by typical PML demyelination with oligodendroglial and astrocytic pathology. The group with early changes revealed widespread, multifocal myelin alterations of a moderate intensity with predominant oligodendroglial abnormalities and less advanced astrocytic changes. Atypical form of the disease was represented by cases with unifocal changes, although containing all key elements of PML pathology. The leading pathological feature of the severe form of the disease consisted in a particular intensity of the demyelination, resulting in tissue destruction often with its cavitation, with typical glial reaction and intense macrophage and lymphocytic infiltration. The other distinguishing feature consisted in strong topographic prevalence of the pathological process either to brain hemispheres or cerebellum. Differences of PML pathology in the course of AIDS as compared with non-AIDS cases are discussed. Due to the relatively high frequency of cases of isolated or strongly predominant involvement of cerebellum, separation of the cerebellar form of the disease has been suggested.