Definition

Progressive Multifocal Leukoencephalopathy (PML) is a rare disease of the white matter of the brain.

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Causes

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 people.

The virus can start to cause problems in people with a weak immune system. It attacks the cells that make the material that insulates nerve cells (neurons).

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
• Certain medicines that treat multiple sclerosis (MS)
• Rare, inherited immunodeficiencies

Symptoms

PML gets worse over time. Problems may be:

• Lack of strength in the arms and legs
• Problems moving
• Changes in behavior and thinking
• Memory problems
• Problems seeing
• Speech problems
• A loss of language
• Sensory loss
• Signs of seizures, such as jerking arm and leg motions

Diagnosis

You will be asked about your symptoms and health history. A physical exam will be done.

An MRI scan will be done to look for damage to the brain.

To confirm PML, your doctor may need:

• Lumbar puncture to look for the virus in the fluid that surrounds the brain
• Brain biopsy to look for the virus in brain tissue

Treatment

There is no cure. The goal of treatment is to strengthen the immune system to slow harm to the body. Choices are:

• Antiretroviral medicine for people who have HIV
• Stopping any medicine that weakens the immune system
• A plasma exchange to quickly remove any medicine that weakens the immune system from the blood

Prevention

The virus that causes PML cannot be prevented. PML may be prevented in people with HIV by taking steps to prevent the immune system from weakening.