Progressive multifocal leukoencephalopathy

PML; John Cunningham virus; JCV; Human polyomavirus 2; JC virus

Progressive multifocal leukoencephalopathy (PML) is a rare infection that damages the material (myelin) that covers and protects nerves in the white matter of the brain.

Gray and white matter of the brain

The tissue called gray matter in the brain and spinal cord is also known as substantia grisea, and is made up of cell bodies. White matter, or substantia alba, is composed of nerve fibers.


Progressive multifocal leukoencephalopathy is an advancing viral inflammation of the white matter of the brain. Immunosuppressed people are more susceptible to this disorder than the general population. Evidence of the disease may be a person's recent loss of coordination and weakness, progressing to a loss of language, visual problems and headaches.



Exams and Tests


Outlook (Prognosis)