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What is PML?

Progressive multifocal leukoencephalopathy (PML) is, in the general population, a rare but serious infection of the central nervous system (CNS) that can and usually does lead to severe disability or death.1 It is caused by the combination of a common infection by a virus known as JC virus, (John Cunningham virus) and additional risk factors that include a weakened immune system and possibly genetic factors.


Although it is not common, PML can occur in a variety of types of patients. It has been seen in patients with:

Patient imageInitial symptoms of PML may include loss of language ability, changes in personality, memory loss, loss of coordination or clumsiness, vision problems, headaches and seizures.4,5 As the disease progresses, symptoms become worse and severe disability or death will often result. If PML is left unmanaged, the mortality rate is 30-50% within the first three months of diagnosis.6 Even when death does not result, it is likely that some significant damage will be permanent.


Review risk factors frequently with your healthcare professional. If you are concerned about PML for any reason, immediately consult your physician.


The PML Consortium encourages patients to review risk factors frequently and remain vigilant in working with their physicians to monitor for signs and symptoms of PML. If you are concerned about PML for any reason, please consult your physician for full background information and a monitoring plan.


Disclaimer: The information on this website is for informational purposes only and is not being provided for the purposes of medical advice. View site Terms of Use.


1 Bruce Brew, Nicholas Davies, et. al. Progressive multifocal leukoencephalopathy and other forms of JC virus disease. Nature Neurology. December 2010; Volume 6p. 667.

2 NINDS Progressive Multifocal Leukoencephalopathy Information Page.  National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/pml/pml.htm. Accessed December 2012.

3 Thomas Weber. Progressive multifocal leukoencephalopathy. Neurol Clin. 2008 Aug;26(3):833-54, x-xi and Brew, 668. For information on specific therapeutics, please refer to the manufacturers’ websites.

4 Progressive multifocal Leukoencephalopathy. MedlinePlus. U.S. National Library of Medicine, National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/000674.htm. Updated February 16, 2012. Accessed September 2012.

5 NINDS Progressive multifocal leukoencephalopathy Information Page. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/pml/pml.htm. Updated September 27, 2011. Accessed September 2012.

6 Brew, 673.