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Progressive Multifocal Leukoencephalopathy


Pronounced: LOO-koh-en-sef-ah-LOP-ah-thee


PML is a rare progressive disease of the nervous system. PML is caused by a viral infection of the cells that produce myelin.

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Causes    TOP

PML is caused by a specific papovavirus, known as John Cunningham (JC) virus. Many people get this infection in childhood. It produces no illness and generally does not infect the nervous system. It reactivates later in life in people who have suppressed immune systems. The virus damages oligodendrocytes, the cells in the central nervous system (CNS) which produce myelin, the material that wraps around nerves. Less myelin around the nerves impairs nerve function.

Risk Factors    TOP

PML is most common in people with suppressed immune systems. Suppressed immune systems may be the result of:

  • HIV/AIDS (most common)
  • Leukemia and lymphoma
  • Organ transplant
  • Cancer
  • Chronic steroid therapy
  • Rare, inherited immunodeficiencies
  • Certain medications, such as natalizumab, a medication used to treat multiple sclerosis (MS)

Symptoms    TOP

Symptoms progress over weeks and may include:

  • Vision problems
  • Speech pronunciation problems
  • Coordination loss
  • Memory loss
  • Weakness in limbs
  • Behavioral changes
  • Changes in thinking
  • A loss of language capability—aphasia
  • Seizures
  • Sensory loss

Diagnosis    TOP

Your doctor will ask about your symptoms and medical history. A physical exam will be done. Tests may include:

  • MRI scan—used to take images of brain structures (key in the diagnosis)
  • Lumbar puncture—to evaluate cerebrospinal fluid
  • Blood and urine tests
  • Brain biopsy

Treatment    TOP

Treatment focuses on strategies to improve the immune system. If you have HIV, your doctor will most likely prescribe medications to treat this condition. If PML has resulted from the drug natalizumab, your doctor will have you stop taking this drug and may recommend a plasma exchange to remove the drug from your blood system.

Prevention    TOP

There are no current guidelines to prevent exposure to the JC virus. If you have a suppressed immune system, follow your treatment plan to minimize your risk.


AIDS Information, Education, Action, Awareness
NORD—National Organization for Rare Disorders


Canadian AIDS Society
CORD—Canadian Organization for Rare Disorders


NINDS progressive multifocal leukoencephalopathy information page. National Institute of Neurological Disorders and Stroke website. Available at
...(Click grey area to select URL)
Updated February 14, 2014. Accessed June 2, 2014.
Progressive multifocal leukoencephalopathy. EBSCO DynaMed Plus website. Available at: http://www.dynamed.... Updated January 8, 2016. Accessed September 26, 2016.
Progressive multifocal leukoencephalopathy (PML). AETC National Resource Center website. Available at:
...(Click grey area to select URL)
Updated May 1, 2013. Accessed June 2, 2014.
Warnke C, Menge T, Hartung HP, et al. Natalizumab and progressive multifocal leukoencephalopathy: what are the causal factors and can it be avoided? Arch Neurol. 2010;67(8):923-930.
Last reviewed January 2018 by Rimas Lukas, MD
Last Updated: 1/11/2018

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