PML is a rare progressive disease of the nervous system. It is caused by a viral infection of the cells that produce myelin.
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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.
PML is most common in people with suppressed immune systems. Suppressed immune systems may be the result of: HIV/AIDS
CancerChronic steroid therapyRare inherited immunodeficiencies
Certain medications, such as
natalizumab, a medication used to treat
Symptoms progress over weeks and may include: Vision problemsSpeech pronunciation problemsCoordination lossMemory lossWeakness in limbsBehavioral changesChanges
A loss of language capability—
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)
—to evaluate cerebrospinal fluid
Blood and urine tests
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
to remove the drug from your blood system.
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.
Progressive multifocal leukoencephalopathy (PML). AETC National Resource Center website. Available at:
http://aidsetc.org/resource/progressive-multifocal-leukoencephalopathy-pml. Updated May 1, 2013. Accessed June 2, 2014.
NINDS progressive multifocal leukoencephalopathy information page. National Institute of Neurological Disorders and Stroke website. Available at
http://www.ninds.nih.gov/disorders/pml/pml.htm. Updated February 14, 2014. Accessed June 2, 2014.
Progressive multifocal leukoencephalopathy. EBSCO DynaMed website. Available at:
http://www.ebscohost.com/dynamed. Updated October 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 June 2015 by Rimas Lukas, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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