Progressive multifocal leukoencephalopathy
PML; John Cunningham virus; JCV; Human polyomavirus 2; JC virus
Progressive multifocal leukoencephalopathy (PML) is a rare infection that damages the material (myelin) that covers and protects nerves in the white matter of the brain.
The tissue called gray matter in the brain and spinal cord is also known as substantia grisea, and is made up of cell bodies. White matter, or substantia alba, is composed of nerve fibers.
Progressive multifocal leukoencephalopathy is an advancing viral inflammation of the white matter of the brain. Immunosuppressed people are more susceptible to this disorder than the general population. Evidence of the disease may be a person's recent loss of coordination and weakness, progressing to a loss of language, visual problems and headaches.
Causes
The John Cunningham virus, or JC virus (JCV), causes PML. JCV is also known as human polyomavirus 2. By age 10, most people have been infected with JCV, but it rarely causes symptoms. The virus remains in the body, but normally is inactive and causes no problems. But people with a weakened immune system are at risk of developing PML. Causes of a weakened immune system include:
- HIV/AIDS (less common now because of better management of HIV/AIDS).
- Medicines that suppress the immune system, including monoclonal antibodies. These medicines are used to prevent organ transplant rejection or to treat multiple sclerosis, rheumatoid arthritis and other autoimmune disorders, and related conditions.
- Cancers, such as leukemia and Hodgkin lymphoma.
Symptoms
Symptoms may include any of the following:
- Loss of coordination, clumsiness
- Loss of language ability (aphasia)
- Memory loss
- Vision problems
- Weakness of the legs and arms that gets worse
- Personality changes
Exams and Tests
Your health care provider will perform a physical exam and ask about symptoms.
Tests may include:
- Brain biopsy (in rare cases)
- Cerebrospinal fluid analysis and blood test for the JCV
- CT scan of the brain
- Electroencephalogram (EEG)
- MRI of the brain
Treatment
In people with HIV/AIDS, treatment to strengthen the immune system can lead to recovery from the symptoms of PML. No other treatments have proved effective for PML. Medicines to treat PML are being developed and may be available in the near future.
Outlook (Prognosis)
PML is a life-threatening condition. Depending on how severe the infection is, up to one half of people diagnosed with PML die within the first few months. Talk to your provider about care decisions.
References
Hirsch HH. Polyomaviruses. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 341.
Tan CS, Koralnik IJ. JC, BK, and other polyomaviruses: progressive multifocal leukoencephalopathy (PML). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 144.
Version Info
Last reviewed on: 3/31/2024
Reviewed by: Joseph V. Campellone, MD, Department of Neurology, Cooper Medical School at Rowan University, Camden, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
