Progressive Multifocal Leukoencephalopathy: PML Facts

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Myelin is a material that insulates and protects the spinal cord and brain’s nerve cells or neurons. Myelin is crucial for the overall health of your brain. Progressive multifocal leukoencephalopathy, otherwise known as PML, is a disease which targets cells that produce myelin. It is a disease of the white matter of the brain.

PML is caused by Polyomavirus JC (often called JC virus). This particular virus is carried by a majority of people and is, in many cases, completely harmless. The danger is for those with lowered immune defenses.

Progressive multifocal leukoencephalopathy is rare, but if there is a situation in which the immune system is greatly compromised, such as in patients with cancer or autoimmune conditions, or if one is being treated with biological therapies which allow JC virus reactivation, then PML becomes a possibility.

Progressive multifocal leukoencephalopathy is not a common disease. It occurs in approximately one in 200,000 people.   In fact, PML is most common among individuals with HIV-1 infection / acquired immune deficiency syndrome (AIDS). Studies show that as many as 5 percent of people infected with HIV-1 eventually develop PML that is an AIDS-defining illness, prior to effective antiretroviral therapy.

Fortunately, however, current HIV therapy using antiretroviral drugs (ART), effectively restores immune system function. This has allowed as many as half of all HIV-PML patients to survive, even though there is a possibility they may sometimes have an inflammatory reaction in the regions of the brain which have been affected by PML.

 To understand the term, let’s break it down.

"Progressive" in PML means that the disease continues to get worse, not better. It can lead to serious complications of the white matter of the brain, and severe brain damage. "Multifocal" means that more than one area of the brain can be affected. Mmultiple parts can be damaged. That being said, individuals can have only one brain lesion instead of several lesions.

“Leukoencephalopathy" means that the disease affects mainly the white matter of the brain or myelin, although there are some rare cases in which the gray matter neurons are also involved.

Due to the fact that PML affects varying locations and varying degrees of intensity from individual to individual, the symptoms of PML will not always be the same. Also, symptoms can change from person to person over the course of days, weeks, or months.

This is all dependent upon the type, location and degree of damage in the brain. However, the most prominent symptoms include:

• progressive weakness
• clumsiness
• changes in vision
• changes in speech
• changes in personality

The quality of life is compromised and PML can be fatal. Diagnosing PML includes doing a biopsy on the brain, combining observations of a progressive course of disease which are consistent with MRI results showing white matter lesions, as well as detecting JC virus in the spinal fluid.

Treatment of PML includes plasma exchange. This treatment accelerates the removal of the therapeutic agents that put patients at risk for PML. For example, in the case of HIV-associated PML, beginning anti-retroviral therapy immediately can benefit people.

The U.S. Food and Drug Administration is also providing special permission for new drugs to be tested on PML patients. Another possibility is now being studied as a possible treatment option for JCV as it seems to be able to suppress JCV by inhibiting viral DNA replication.

The name of this drug is Hexadecyloxypropyl-Cidofovir, or CMX001. The best available therapy is reversal of the immune-deficient state, since there are no effective drugs that block virus infection without toxicity.

Depending on the severity of the underlying disease and treatment received, PML has a mortality rate of 30-50 percent in the first few months following diagnosis but. Survival can also mean suffering with neurological damage and impairments.

The National Institute of Neurological Disorders and Stroke (NINDS) and other institutes of the National Institutes of Health (NIH) conduct research related to PML in laboratories at the NIH, and support additional research through grants to majorresearch institutions across the country. Much of this research focuses on finding better ways to prevent, treat, and ultimately cure disorders such as PML.

Sources:

National Institute of Neurological Disorders and Stroke. NINDS Progressive Multifocal Leukoencephalopathy Information Page. What is Progressive Multifocal Leukoencephalopathy? Retrieved from the internet on November 13, 2011.
http://www.ninds.nih.gov/disorders/pml/pml.htm

WebMD. Brain and Nervous System Health Center.
Progressive Multifocal Leukoencephalopathy. Retrieved from the internet on November 13, 2011.
http://www.webmd.com/brain/progressive-multifocal-leukoencephalopathy

Aimee Boyle is a regular contributor to EmpowHER

Reviewed November 17, 2011
by Michele Blacksberg RN
Edited by Jody Smith

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