| Abstract: | Progressive multifocal leukoencephalopathy: ultrastructural findings in two brain biopsies Cerebral biopsies from two patients with progressive multifocal leukoencephalopathy due to SV40 (Case 1) and JC viruses (Case 2) have been examined by light and electron microscopy. No features permitting the morphologic differentiation of the diseases caused by the two agents were found. In the first case, intranuclear viral inclusions were seen in satellite oligodendrocytes in the cerebral cortex as well as in oligodendrocytes in the white matter. In this case demyelination developed in the absence of an inflammatory response. Extensive oligodendrocyte proliferation was evident, and phagocytosed myelin debris was found in both oligodendrocytes and astrocytes. In the second case extensive perivascular and tissue infiltration with plasma cells and evidence of viral multiplication in astrocytes were found. Demyelination occurred in the absence of macrophages in the first case which supports the conclusion that the demyelination in PML is due to the cytolytic effect of the virus on oligodendrocytes and is not an immunopathologic process. |
