JC Virus (JCV)
The JC virus or JCV is an infection present in about 85 percent of people. Most people acquire it sometime during childhood. It lives in a latent harmless state in the kidneys and the gastrointestinal tract in people with healthy immune systems. The virus was named for the person in whom it was diagnosed in 1971, John Cunningham.
JCV becomes a life-threatening virus in people whose immune systems are compromised. The virus is activated and migrates through the blood stream to the brain. The virus causes progressive multifocal leukoencephalopathy (PML), a rare, but frequently deadly condition that destroys myelin, a protective covering of nerve cells in the brain. PML usually progresses to death or severe disability within days, weeks, or sometimes months.
The symptoms of PML worsen over time. They include headaches, increasing weakness of the arms and legs, clumsiness and lack of coordination, vision problems, memory loss, and aphasia (loss of the ability to speak, listen, read, and write). The condition is seen mainly in patients with HIV, but does occur in others as well. PML is found in patients, such as the following, whose immune systems are depressed:
- People with AIDS
- Patients who have had organ transplants and are taking immunosuppressive drugs
- Persons with systemic lupus erythematosus
- Patients with certain cancers and other diseases, including Hodgkin's disease, Lymphoma and Sarcoidosis
- Persons who have been treated with drugs that suppress the immune system, such as Raptiva®, that was prescribed to treat plaque psoriasis. Raptiva® was pulled from the market by its maker Genentech when people on the drug began to develop PML.
There is no known treatment or cure for PML. In 2009, the U.S. Food and Drug Administration (FDA) said, "the risk that an individual patient taking Raptiva® will develop PML is rare and is generally associated with long-term use. Generally, PML occurs in people whose immune systems have been severely weakened and often leads to an irreversible decline in neurologic function and death."
The disease is diagnosed by its symptoms as well as by using:
- Tests of the cerebrospinal fluid for the present of JCV. This is the best way to obtain a definitive diagnosis
- Computed tomography (CT scan)
- MRI (magnetic resonance imaging) of the brain