Progressive Multifocal Leukoencephalopathy (PML) is a rare disease that gets worse over time. It harms brain cells.

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PML is caused by an infection by a specific virus. Many people get this virus as a child, but do not get sick until later. It stays in the body and does not cause problems in most.

If the immune system becomes weak, the virus can start to cause problems. It attacks the coating around the brain cells. Messages can't be passed between cells without this coating.

Risk Factors

PML is most common in people who have problems with their immune system. These problems may be from:

  • HIV/AIDS (most common)
  • Leukemia and lymphoma
  • Organ transplant
  • Cancer
  • Long term use of steroid medicines
  • Rare, inherited immunodeficiencies
  • Certain medicines that treats multiple sclerosis (MS)


You will feel worse over time. You may have:

  • Lack of strength in the arms and legs
  • Problems with movement
  • Changes in behavior and thinking
  • Problems remembering things
  • Problems seeing
  • Speech problems
  • A loss of language
  • Sensory loss
  • Seizures


Your doctor will ask about your symptoms and health history. A physical exam will be done.

An MRI scan will be needed to see any damage to the brain cells. This may help to rule out other causes.

To confirm PML, your doctor may need:

  • Brain biopsy —to check for changes in cells
  • Lumbar puncture —to look for the virus in the fluid that surrounds the brain


There is no way to treat the infection or PML. Treatment is aimed at ways to make your immune system better to stop further harm. It will depend on your health needs, but here are some methods:

  • If you have HIV, antiretroviral medicine will be started.
  • If medicine caused PML, your doctor will have you stop taking it.

Harm to the cells can't be fixed. This can cause severe disability.


You can’t prevent the virus that causes PML. Keep your immune system as healthy as you can. It may help prevent certain infections.

Revision Information

  • Reviewer: EBSCO Medical Review Board Rimas Lukas, MD
  • Review Date: 05/2018 -
  • Update Date: 06/25/2018 -