[A case of progressive multifocal leucoencephalopathy during chronic lymphocytic leukaemia].

We report here a case of PML in the course of untreated chronic lymphocytic leukaemia. The diagnosis of PML was based on the presence of typical histologic findings in the white matter: focal demyelination, abnormal oligodendroglia with basophilic intranuclear inclusions and enlarged bizarre astrocytes. It was confirmed by immunohistochemistry which revealed JC papova-virus antigens in brain tissue and by in-situ hybridization which showed JC virus genomic DNA in oligodendroglial nuclei. Virus particles in the nuclei of abnormal oligodendrocytes and astrocytes were demonstrated by thin-section electron-microscopy.