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Progressive Multifocal Leukoencephalopathy

Progressive multifocal leukoencephalopathy, or PML, is a rare, life-threatening infectious disease of the brain. It is caused by the reactivation of a common virus, polyomavirus JC, that infects and destroys parts of the brain.

Around 85 percent of the adult population have antibodies to JC virus, a virus typically contracted in childhood. Most people infected with JC virus never have a problem.

However, in a small percentage of people who have this virus, particularly those with compromised immune systems, JC virus can be reactivated and cause PML.

PML symptoms

The symptoms of PML vary, depending on where the virus affects the brain and the extent of the damage.

These are some of the more frequent symptoms:

  • A lack of control during movement of the voluntary muscles (ataxia), particularly in the limbs or when walking
  • Weakness on one half of the body (hemiparesis) or in one limb (monoparesis)
  • Vision changes, such as blindness in half of your field of vision (hemianopia) or double vision (diplopia)
  • Altered mental state

Risk factors for PML

Having a compromised immune system is the greatest risk factor for developing PML. The following contribute to a compromised immune system and, although rare, can be risk factors for developing PML:

  • Having untreated AIDS
  • Use of monoclonal antibodies, particularly those used to treat multiple sclerosis (natalizumab) and lymphomas (rituximab)
  • Use of long-term immune-suppressing drugs, such as those frequently used for organ transplants, as well as patients with rheumatoid arthritis and systemic lupus erythematosus

How can I get help for progressive multifocal leukoencephalopathy?

If you have any of the above risk factors without symptoms and are concerned that you may develop PML, talk to your primary care doctor. He or she may refer you to a neurologist who specializes in neuroinfectious diseases.

Care for progressive multifocal leukoencephalopathy at Rush


A PML diagnosis can be made based on the neurological exam, combined with a magnetic resonance imaging (MRI) and the detection of JC virus in the cerebral spinal fluid via a spinal tap or through a brain biopsy.


There is currently no treatment that directly targets JC virus. Therefore, all treatments focus on rebuilding a PML patient's immune system.

The treatment course will depend on the issues contributing to the reactivation of JC virus, such as the following examples:

  • Antiretroviral therapy for HIV/AIDS patients with PML
  • Stopping the drug natalizumab for MS patients with PML, and undergoing plasma exchange to speed removal of the drug from their bodies 

Why choose Rush for PML care

  • Neuroinfectious disease specialists at Rush are experts at recognizing and treating both the immediate nature of PML and the long-term neurologic complications of any underlying conditions leading to its development.
  • Rush’s neurological sciences and neurological surgery programs are consistently rated among the best in the country by U.S. News & World Report.
  • As an academic medical center, Rush offers the opportunity to participate in clinical research on PML that may not otherwise be available anywhere else, in addition to best available treatment options.

Departments and programs that treat this condition