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Progressive Multifocal Leukoencephalopathy

  • Definition

    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

    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

    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

    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

    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

    Treatment focuses on strategies to improve the immune system. If you have HIV, your doctor will most likely prescribe antiretroviral 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

    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 Updated February 14, 2014. Accessed June 2, 2014.

    Progressive multifocal leukoencephalopathy. EBSCO DynaMed website. Available at: Updated October 1, 2013. Accessed June 2, 2014.

    Progressive multifocal leukoencephalopathy (PML). AETC National Resource Center website. Available at: 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.

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