Progressive Multifocal Leukoencephalopathy (PML) is a rare, opportunistic infection of the central nervous system (CNS) caused by a reactivation of the JC (John Cunningham) virus. PML is a brain disorder that affects the white matter part of the brain, specifically targeting the cells that make myelin (oligodendrocytes). A majority of adults have been exposed to the JC Virus at some point in their lives. However, PML is a very rare disease which typically does not affect healthy individuals.
Individuals with autoimmune diseases such as MS, RA, lupus, and
vasculitis are at increased risk of PML, primarily due to some of the
drug therapies used to treat these autoimmune diseases which alter the
immune system and may allow a reactivation of the JC virus. However,
cases of PML in patients using select disease-modifying drugs is still
very rare. Even more rarely, PML has occurred in RA patients who
haven’t taken any disease-modifying drugs or biologics.
Read these posts in their entirety:
Progressive Multifocal Leukoencephalopathy: What is PML? Part One
PML Diagnosed in Autoimmune Rheumatic Diseases, Part Two