neurologic disorders
Progressive Multifocal Leukoencephalopathy (PML)
Key Points
Reactivation of the ubiquitous JC virus, usually due to impaired cell-mediated immunity, leads to PML. PML commonly causes clumsiness, hemiparesis, aphasia, dysarthria, hemianopia, and cognitive impairment. Do MRI and test CSF for JC virus DNA in patients who have impaired cell-mediated immunity and unexplained progressive brain dysfunction. Treat patients supportively, and manage underlying disorders as indicated (eg, by stoppingnatalizumab, another immunomodulatory drug, or an immunosuppressant or, in patients with AIDS, by initiating antiretroviral therapy and watching closely for development of immune reconstitution inflammatory syndrome). Limited data suggest that treatment withpembrolizumabornivolumabmay decrease viral load in the CSF, increase antiviral cellular immune activity, and lead to clinical improvement. 