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

Causes

The JC virus (JCV) causes PML. By age 10, most people have been infected with this virus, but it hardly ever causes symptoms.

Anyone with a weakened immune system, however, are at greater risk of developing PML. Causes of a weakened immune system include:

• AIDS (less common now because of better AIDS treatments)
• Certain medications used to treat multiple sclerosis, rheumatoid arthritis, and related conditions
• Leukemia and lymphoma

Symptoms

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

Exams and Tests

Tests may include:

• Brain biopsy (rare)
• Cerebrospinal fluid test for the JCV
• CT scan of the brain
• Electroencephalogram (EEG)
• MRI of the brain

Treatment

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.

Outlook (Prognosis)

PML is a life-threatening condition. Talk to your doctor about care decisions.

Alternative Names

PML