Progressive Multifocal Leukoencephalopathy

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

  • Causes

    PML is caused by a specific papovavirus, known as 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. This impairs nerve function.

  • Definition

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

    The Neuron
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  • 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

  • Prevention

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

  • 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

  • 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.