Progressive multifocal leucoencephalopathy (PML) is a rare infectious disease of the brain, provoked by the JC virus. It usually occurs in subjects with impaired immune system as during HIV infection. To date, there is no specific antiviral treatment susceptible to cure PML. But it was shown in the setting of HIV-related PML, that combination antiretroviral therapy allows a restoration of the immune system and then might stop the progression of PML.