Progressive Multifocal Leukoencephalopathy (PML) By John E Greenlee, MD, University of Utah Health Reviewed / Revised Mar 2022 | Modified Sep 2022 View Patient Education Etiology Symptoms and Signs Diagnosis Treatment Key Points Topic Resources Progressive Multifocal Leukoencep.. Progressive multifocal leukoencephalopathy (PML) is caused by reactivation of the JC virus.