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Progressive Multifocal Leukoencephalopathy (PML)


John E. Greenlee

, MD, University of Utah Health

Last full review/revision Jul 2020| Content last modified Jul 2020

Progressive multifocal leukoencephalopathy is a rare infection of the brain that is caused by the JC (John Cunningham) virus.

  • People with a weakened immune system are most likely to get the disorder.

  • People may become clumsy, have trouble speaking, and become partially blind, and mental function declines rapidly.

  • Death usually occurs within 9 months.

  • Imaging of the head and a spinal tap are done.

  • Treating the disorder that weakened the immune system may help people live longer.

Progressive multifocal leukoencephalopathy results from infection by the JC virus. The JC virus is often acquired during childhood. Most adults have been infected with the JC virus but do not develop the disorder.

The virus appears to remain inactive until something (such as a weakened immune system) allows it to be reactivated and start to multiply. Thus, the disorder affects mainly people whose immune system has been weakened by a disorder (such as leukemia Overview of Leukemia Leukemias are cancers of white blood cells or of cells that develop into white blood cells. White blood cells develop from stem cells in the bone marrow. Sometimes the development goes awry... read more , lymphoma Overview of Lymphoma Lymphomas are cancers of lymphocytes, which reside in the lymphatic system and in blood-forming organs. Lymphomas are cancers of a specific type of white blood cells known as lymphocytes. These... read more Overview of Lymphoma , or AIDS Acquired immunodeficiency syndrome (AIDS) Human immunodeficiency virus (HIV) infection is a viral infection that progressively destroys certain white blood cells and can cause acquired immunodeficiency syndrome (AIDS). HIV is transmitted... read more Acquired immunodeficiency syndrome (AIDS) ) or by drugs that suppress the immune system (Immunosuppressants Suppression of the Immune System Transplantation is the removal of living, functioning cells, tissues, or organs from the body and then their transfer back into the same body or into a different body. The most common type of... read more ) or that modify the immune system (immunomodulators). Such drugs include those used to prevent rejection of transplanted organs or to treat cancer or autoimmune disorders Autoimmune Disorders An autoimmune disorder is a malfunction of the body's immune system that causes the body to attack its own tissues. What triggers autoimmune disorders is not known. Symptoms vary depending on... read more , such as systemic lupus erythematosus Treatment Systemic lupus erythematosus is a chronic autoimmune inflammatory connective tissue disorder that can involve joints, kidneys, skin, mucous membranes, and blood vessel walls. Problems in the... read more Treatment (lupus) or multiple sclerosis Multiple Sclerosis (MS) In multiple sclerosis, patches of myelin (the substance that covers most nerve fibers) and underlying nerve fibers in the brain, optic nerves, and spinal cord are damaged or destroyed. The cause... read more . These drugs include natalizumab and rituximab, which are monoclonal antibodies, and brentuximab vedotin, which is an anticancer drug combined with a specific antibody Antibodies One of the body's lines of defense (immune system) involves white blood cells (leukocytes) that travel through the bloodstream and into tissues, searching for and attacking microorganisms and... read more Antibodies that targets cancer cells.

Symptoms of PML

The JC virus appears to cause no symptoms until it is reactivated.

Symptoms of progressive multifocal leukoencephalopathy may begin gradually and usually worsen progressively. They vary depending on which part of the brain is infected.

The first symptoms may be clumsiness, weakness, or difficulty speaking or thinking. As the disorder progresses, many people develop dementia and become unable to speak. Vision may be affected. People with progressive multifocal leukoencephalopathy eventually become bedbound. Rarely, headaches and seizures occur, mainly in people with AIDS.

Death is common within 1 to 9 months of when symptoms start, but a few people survive longer (about 2 years).

People who develop progressive multifocal leukoencephalopathy while taking a drug that suppresses the immune system (such as natalizumab) may recover once the drug is stopped. However, many continue to have problems related to the infection.

Diagnosis of PML

  • Magnetic resonance imaging

  • A spinal tap

Unexplained, progressively worsening symptoms in people with a weakened immune system suggest progressive multifocal leukoencephalopathy.

Magnetic resonance imaging (MRI) of the head is done. It can usually detect abnormalities that suggest the diagnosis.

A spinal tap Spinal Tap Diagnostic procedures may be needed to confirm a diagnosis suggested by the medical history and neurologic examination. Electroencephalography (EEG) is a simple, painless procedure in which... read more Spinal Tap (lumbar puncture) is done to obtain a sample of cerebrospinal fluid (the fluid that flows through the tissues that cover the brain and spinal cord). The polymerase chain reaction (PCR) technique, which produces many copies of a gene, is used to detect the JC virus's DNA in the cerebrospinal fluid.

Treatment of PML

  • If the cause is a weakened immune system, treatment of the cause

No treatment for progressive multifocal leukoencephalopathy has proved effective. However, if the disorder that has weakened the immune system is treated, people survive longer. For example, if the cause is AIDS, antiretroviral therapy Drug Treatment of Human Immunodeficiency Virus (HIV) Infection Antiretroviral drugs used to treat human immunodeficiency virus (HIV) infection aim to do the following: Reduce the amount of HIV RNA (viral load) in the blood to an undetectable amount Restore... read more is used.

If people are taking immunosuppressants or other drugs that affect the immune system (such as natalizumab), stopping the drugs may cause progressive multifocal leukoencephalopathy to subside. Then plasma exchange Plasma exchange In apheresis, blood is removed from a person and then returned after substances are removed from it. Apheresis can be used to Obtain healthy blood components from a donor to transfuse to a person... read more is used to remove the drug from the blood, particularly when the drug is natalizumab (used to treat multiple sclerosis).

People who are treated with antiretroviral therapy or who stop taking immunosuppressants may develop immune reconstitution inflammatory syndrome (IRIS) Immune reconstitution inflammatory syndrome Antiretroviral drugs used to treat human immunodeficiency virus (HIV) infection aim to do the following: Reduce the amount of HIV RNA (viral load) in the blood to an undetectable amount Restore... read more . In this disorder, the recovering immune system launches an intense attack against the JC virus, which can make symptoms temporarily worse. Corticosteroids may help relieve symptoms.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Brentuximab vedotin
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