Progressive Multifocal Leukoencephalopathy

Abstract

Progressive multifocal leukoencephalopathy (PML) is a severe demyelinating disease of the central nervous system that is caused by reactivation of the polyoma virus JC (JC virus). Asymptomatic primary infection with JC virus occurs in childhood and antibodies can be found in 86% of adults. In most individuals JC virus remains latent in kidneys and lymphoid organs, but in the context of profound immunosuppression JC virus can reactivate, spread to the brain, and induce a lytic infection of oligodandrocytes, which are the CNS myelin producing cells. The diagnostic hallmark of progressive multifocal leukoencephalopathy is the presence of oligodandrocytes with enlarged nuclei containing intra nuclear amphophilic inclusions. Sometimes these inclusions are also identified in astrocytes. This is a case of progressive multifocal leucoencephalopathy in a 67-year-old male with a background of chronic lymphocytic leukaemia. The histopathological examination of the brain biopsy revealed intranuclear inclusion present not only in the oligodandrocytes and granule neurons of cerebellum, but also in the purkinjee cells. In addition, the plasma cells demonstrated mono-typic, kappa light chain restriction.