[Review of progressive multifocal leukoencephalopathy].

Progressive multifocal leukoencephalopathy (PML) is a fatal demyelinating disease of the central nervous system caused by a reactivation of the JC virus (JCV). PML occurs almost exclusively in the setting of cellular immune deficiency and its prevalence has recently increased greatly, in line with the AIDS (acquired immunodeficiency syndrome) epidemic in Western countries. A Japanese epidemiological survey showed an increasing trend in the number of AIDS-PML cases. To date, there are no effective and specific therapies for PML. As patients with AIDS-PML may benefit from combined antiretroviral therapy, efforts to improve the immune status of such patients is therefore considered to be a key factor in achieving a successful outcome for PML cases. However, PML deficits are nevertheless expected to be permanent and most cases of PML result in death within a few months. It is therefore hoped that improvements in diagnostic modalities can be made which can eventually allow for the earlier detection of PML while, at the same time, improved curative therapies for PML can also be developed in the near future.