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.
(See also Overview of Brain Infections.)
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, lymphoma, or end-stage HIV infection [AIDS]) or by medications that suppress the immune system (immunosuppressants) or that modify the immune system (immunomodulators). Such medications include those used to prevent rejection of transplanted organs or to treat cancer or systemic rheumatic disorders, such as systemic lupus erythematosus (lupus) or multiple sclerosisantibody that targets cancer cells.
Symptoms of PML
The JC virus appears to cause no symptoms until it is reactivated.
Symptoms of PML 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 PML eventually become bedbound. Rarely, headaches and seizures occur, mainly in people with end-stage HIV infection.
Death is common within 1 to 9 months of when symptoms start, but a few people survive longer (about 2 years).
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 (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 PML has proved effective. However, if the disorder that has weakened the immune system is treated, people survive longer. For example, if the cause is end-stage HIV infection, antiretroviral therapy is used.
People who are treated with antiretroviral therapy or who stop taking immunosuppressants may develop immune reconstitution inflammatory syndrome (IRIS). 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.
immune checkpoint inhibitors) may help lessen symptoms and slow progression of progressive multifocal leukoencephalopathy, but these effects have not been confirmed.
