PROGRESSIVE MULTIFOCAL LEUKOENCEPHALOPATHY

Progressive multifocal leucoencephalopathy (PML) is a rarely occurring demyelinating disease of the central nervous system caused by a neuro tropic papovavirus named JC virus (JCV). The most frequently affected regions are the cerebral hemispheres, especially the parietooccipital region, followed by the cerebellum and brain stem. The disease occurs predominantly in individuals with an immunocompromised state and impai red cellular mediated immunity (CMI) due to other underlying illness. More extensive use of irradiation and immunosuppressive therapy in rel ation to increased transplantational activities as well as treatment o f autoimmune diseases and malignancies, in addition to the appearance of the acquired immunodeficiency syndrome (AIDS) as a consequence of i nfection with the human immunodeficiency virus (HIV), has caused a con siderable increase in the occurrence of PML. The course of the disease is still most often rapidly progressive and fatal, but several cases with prolonged survival and even remission have been reported, and var ious antiviral treatments have been tried. The only drug that until no w has shown favourable results is cytosine arabinoside. In HIV-infecte d PML-patients immunomodulation with AZT/zidovudine may alleviate the course and improve the prognosis in some patients. Suspicion of PML sh ould lend to an extensive immunological investigation before consideri ng of brain biopsy, which is still the only specific rest. On the basi s of the increased frequency of PML in relation to HIV-infection, it i s likely that our knowledge of the pathogenetic aspects will increase, which, hopefully, may lead to an effective therapeutic strategy.