Progressive multifocal leukoencephalopathy (PML) is a rare inflammatory disorder that causes damage to the material (myelin) that covers nerves. The nerve damage related to PML occurs within the white matter of the brain.

PML is caused by the JC virus (JCV). This virus is found in a lot of people, but usually does not cause symptoms. However, it triggers PML in people who have poor immune function (immunocompromised).

The disease occurs in 4% of adults with AIDS.

Symptoms and signs include loss of coordination, clumsiness, memory loss, progressively worsening weakness of the legs, and to a lesser extent, arms.

Other signs may include loss of language capability (aphasia), visual field defects, and headaches.

• Cytology exam of the urine
• CT scan
• MRI
• Electroencephalography, a test to look at brain waves

Treatment consists of anti-viral and other medications.

PML is almost always deadly. Most patients die within 3 to 6 months.

Mandell GL, Bennett JE, Dolin R. Principles and Practice of Infectious Diseases. 5th ed. London: Churchill Livingstone; 2000:1856-1861.

Cohen J, Powderly WG. Infectious Diseases. 2nd ed. New York, NY: Elsevier; 2004:2046.