The clinical presentation in immunocompromised individuals,1, 2 white matter lesions with little or no enhancement/mass effect on neuroimaging studies,7, 8, 17 detection of variant JCV in the CSF, cytological and histological recognition of ground‐glass nuclei in both JCV‐infected oligodendrocytes and JCV‐infected astrocytes, and immunohistochemical detection, in particular, of SV40‐immunoreactivity or even p53‐immunoreactivity, strongly suggest the diagnosis of PML. Here, TP53 is linked to progressive multifocal leukoencephalopathy.