Progressive multifocal leukoencephalopathy (PML) attacks the white matter of the myelin which is the oily covering of the nerve cells in the brain and spinal cord. Myelin is also called central nervous system (CNS) white matter.
To better understand the nature of this disease, let's try to understand the meaning of the name. "Progressive" means it will get worse. "Multifocal" indicates it is found in more than one location in the brain. "Leuko-" means white or clear. "-Encephalopathy" refers to any disorder or disease of the brain.
So progressive multifocal leukoencephalopathy is a disease of the brain that affects the white matter of the myelin in many areas, causing damage to the central nervous system. It's a disease that starts out bad and will probably get worse.
Progressive multifocal leukoencephalopathy is caused by a virus called the polyomavirus JC. It also is known as JC virus (JCV).
Its name was derived from the initials of the first patient who was known to have suffered the effects of the virus. The JC virus actually infects about 85 percent of the population but it usually will not cause any problems.
The people who are most at risk are those who have a weakened immune system. Cancers such as Hodgkin's disease, leukemia, lymphoma and sarcoidosis can weaken the immune system. Some of the medications that are used in the treatment of such diseases as multiple sclerosis and rheumatoid arthritis can also weaken the immune system.
Organ transplant recipients who have been taking any immuno-suppressant medications may also be vulnerable to ending up with a weakened immune system, as are people who are on corticosteroid therapy. Those individuals who have acquired immune deficiency syndrome (AIDS) are the ones who are most likely to succumb to PML.
Symptoms of progressive multifocal leukoencephalopathy include headaches, weakness in arms and legs, and problems with vision. The individual may become unable to speak, and may lose their coordination, becoming clumsy in their movements.
These symptoms are caused by an infection that destroys the white matter of the myelin in a number of areas in the brain.