The mission of this international registry is to collect information about progressive multifocal leukoencephalopathy (PML) to improve knowledge and further research on this rare disease. We plan to collect data worldwide on incidence, risk factors, disease course, and laboratory and imaging findings. Information obtained from this registry has the potential to assist in developing strategies for treatment and risk mitigation of PML.


Doctor with MS Patient Progressive multifocal leukoencephalopathy (PML) is a relatively rare demyelinating disease caused by the human polyomavirus JCV following reactivation from latent tissues and entry into the central nervous system. JCV is a common virus that infects a majority of people based on antibody studies. Most people who have come in contact with JCV clear the infection through their immune system although some individuals become latently infected. However, in patients with compromised immunity, JCV can traffic to the brain and cause PML. The disease can occur in people who receive medications that alter the immune system, for example to treat immune mediated diseases like multiple sclerosis, Crohn’s disease, or as part of the medical regimen after organ transplantation. It can also rarely occur in patients with cancer, such as Hodgkin’s lymphoma. PML is most common among individuals who are infected with HIV. Studies estimate that prior to effective antiretroviral therapy, as many as 5 percent of people with AIDS eventually developed PML. The symptoms of PML are the result of the loss of white matter (which is made up of myelin, a substance theat surrounds and protects nerve fibers) in multiple areas of the brain. Without the protection of myelin, nerve signals can’t travel successfully from the brain to the rest of the body. Symptoms associated with PML can be diverse, since they are related to the location and amount of damage in the brain. The most common symptoms are cognitive problems, weakness, visual deficits, speech impairment or personality changes. Seizures can also occur. Symptoms typically evolve over the course of several weeks and can lead to significant disability or even death. The diagnosis of PML can be made based on clinical symptoms, findings on magnetic resonance image (MRI) scan of the brain and detection of JCV DNA in cerebrospinal fluid. In some cases a brain biopsy may be needed for confirmation of the diagnosis.

NINDS708-332-0776908-788-7666Usa.gov Logo