PROGRESSIVE multifocal leukoencephalopathy is a rare demyelinating disease first described in 1958 by Astrom et al.1 Since then, close to 50 cases have been reported or reviewed.2-16 With few exceptions, this demyelinating process is observed in patients with chronic diseases of the reticuloendothelial system, most commonly in leukemias and lymphomas. It has also been described in association with other neoplasms.
The lesions consist of patchy foci of demyelination distinguished by the presence of bizarre astrocytes and other glial cells believed to be oligodendrocytes which contain intranuclear inclusions. In 1965, Zu Rhein and Chou,11 using thin section electron microscopy, were able to show that the intranuclear inclusions corresponded to large collections of virus-like particles. Later studies, including those employing the negative staining techniques for electron microscopy, suggested the close similarity between these particles and those of the polyoma SV40 subgroup of the papova viruses. Up to the present
Morecki R, Porro RS. Progressive Multifocal LeukoencephalopathyIdentification of Virions in Paraffin-Embedded Tissues. Arch Neurol. 1970;22(3):253–258. doi:10.1001/archneur.1970.00480210063008