Progressive Multifocal Leukoencephalopathy (PML)
Progressive multifocal leukoencephalopathy (PML) is a neurological disorder characterized by destruction of the myelin, an oily substance that helps protect nerve cells in the brain and spinal cord, also known as central nervous system (CNS) white matter. It is caused by a virus called JC virus (JCV), named after the initials of the patient in whom it was first discovered. The virus is widespread, found in at least 85% of the general adult population. It remains inactive in healthy individuals and causes disease only when the immune system has been severely weakened, such as in people with HIV/AIDS, or hematological malignancies, and in organ transplant recipients who receive immuno- suppressant medications to avoid rejection of the transplanted organ. Altogether, PML occurs in approximately one in 200,000 people.
The term "progressive" in PML means that the disease continues to get worse and often leads to serious brain damage. The term "multifocal" means that JCV causes disease in multiple parts of the brain. However, it is possible for an individual with PML to have only one brain lesion instead of several lesions. The term "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 is also involved.
Is there any treatment?
Currently, the best available therapy is reversal of the immune-deficient state, since there are no effective drugs that block virus infection without toxicity. Reversal may be achieved by using plasma exchange to accelerate the removal of the therapeutic agents that put patients at risk for PML. In the case of HIV-associated PML, immediately beginning anti-retroviral therapy will benefit most individuals. Several new drugs that laboratory tests found effective against infection are being used in PML patients with special permission of the U.S. Food and Drug Administration. Hexadecyloxypropyl-Cidofovir (CMX001) is currently being studied as a treatment option for JVC because of its ability to suppress JVC by inhibiting viral DNA replication.
What is the prognosis?
In general, PML has a mortality rate of 30-50 percent in the first few months following diagnosis but depends on the severity of the underlying disease and treatment received. Those who survive PML can be left with severe neurological disabilities.
What research is being done?
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 :
Annals of Neurology (Author[s]: Mateen, F. J.; Muralidharan, R.; Carone, M.; Van De Beek, D.; Harrison, D. M.; Aksamit, A. J.; Gould, M. S.; Clifford, D. B. et al)
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