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Progressive multifocal leukoencephalopathy

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 John Cunningham virus, or JC virus (JCV) causes PML. By age 10, most people have been infected with this virus. But it hardly ever causes symptoms. But, people with a weakened immune system are at risk of developing PML. Causes of a weakened immune system include:

  • HIV/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.
  • Cancers, such as leukemia and Hodgkin lymphoma.


Symptoms may include any of the following:

  • Loss of coordination, clumsiness
  • Loss of language ability (aphasia)
  • Memory loss
  • Vision problems
  • Weakness of the legs and arms that gets worse
  • Personality changes

Exams and Tests

The health care provider will perform a physical exam and ask about symptoms.

Tests may include:


In people with HIV/AIDS, treatment to strengthen the immune system can lead to recovery from the symptoms of PML. No other treatments have proved effective for PML.

Outlook (Prognosis)

PML is a life-threatening condition. Depending on how severe the infection is, up to one half of people diagnosed with PML die within the first few months.Talk to your provider about care decisions.

Alternative Names

PML; John Cunningham virus; JCV


Berger JR, Nath A. Cytomegalovirus, Epstein-Barr virus, and slow virus infections of the central nervous system. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 370.

Tan CS, Koralnik IJ. JC, BK, and other polyomaviruses: progressive multifocal leukoencephalopathy (PML). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 147.

Review Date 2/27/2016

Updated by: Amit M. Shelat, DO, FACP, Attending Neurologist and Assistant Professor of Clinical Neurology, SUNY Stony Brook, School of Medicine, Stony Brook, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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