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.
The JC virus (JCV) causes PML. By age 10, most people have been infected with this virus. But it hardly ever causes symptoms. However, persons with a weakened immune system are at risk of developing PML. Causes of a weakened immune system include:
AIDS (less common now because of better AIDS treatments)
Certain medicines that suppress the immune system. Such medicines may be used to prevent organ transplant rejection or to treat multiple sclerosis, rheumatoid arthritis, and related conditions.
In people with AIDS, treatment to strengthen the immune system can lead to recovery from the symptoms of PML. No other treatments have proved effective for PML.
PML is a life-threatening condition. Talk to your doctor about care decisions.
Tan CS, Koralnik IJ. JC, BK, and other polyomaviruses: progressive multifocal leukoencephalopathy. In: Mandell GL, Bennett JE, Dolin R. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, PA: Elsevier Churchill-Livingstone; 2009:chap 145.
Joseph V. Campellone, M.D., Division of Neurology, Cooper University Hospital, Camden, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.