Drug–associated progressive multifocal leukoencephalopathy

Abstract

Progressive multifocal leukoencephalopathy (PML) is a neuroinfectious disease caused by the JC virus, and there are no established treatments for PML. Previously, most cases of PML were associated with severe complications such as acquired immunodeficiency syndrome (AIDS) and cancers. Recently, PML has been attracting attention in drug–associated cases without severe complications. One of the most important drugs among drug–associated PML is natalizumab, a disease modifying drug for multiple sclerosis (MS). Recently, cases with drug–associated PML related to other drugs have been reported, and those drugs have been classified according to risk levels for PML. When following up patients receiving PML–risk medications, it is important to suspect and diagnose PML at an early stage, as earlier intervention for drug–associated PML can lead to better patient outcomes. Drug–associated PML often shows abnormal findings on MRI before the onset of symptoms ; therefore, routine and frequent MRI imaging is required in patients receiving PML–risk medications. It is also important to understand the imaging characteristics of PML, as drug–associated PML has been reported to have slightly different MRI findings than PML in patients with AIDS or cancer. As such, careful follow–up in patients receiving PML–risk medications is warranted.