Checkpoint inhibitors and progressive multifocal leukoencephalopathy: friends of foes?

Progressive multifocal leukoencephalopathy (PML) has evolved in the last decade from a disorder of acquired immune deficiency syndrome (AIDS) patients into a rare but fatal complication of several life-saving therapeutics (ranging from rituximab in non-Hodgkin lymphomas to natalizumab in multiple sclerosis). PML is linked to opportunistic reactivation of the latent human JC polyomavirus (JCV), which leads to emergence of neurotropic strains causing brain demyelination.