Our case may also imply that the PML-IRIS phenomenon seems to start independently of the usage of Fingolimod, suggesting that lymphocytic cellular host-defence against JCV reactivation might not be (totally) impaired during Fingolimod treatment [13]; Fingolimod reduced CSF CD4+ T cells and B cells. This evidence concerns the gene CD4 and progressive multifocal leukoencephalopathy.