Progressive Multifocal Leukoencephalopathy

What is progressive multifocal leukoencephalopathy (PML)?

Progressive multifocal leukoencephalopathy is a neurological disorder in which myelin, the protective covering of nerve cells of the central nervous system, is destroyed. It is a progressive disorder and can lead to brain damage. While it usually sees multiple lesions in the brain, some people only have one. John Cunningham (JC) virus is the cause.

It occurs in one of every 200,000 people, and it is believed that about 4,000 people develop PML is the U.S. and Europe each year. It is tied to a major weakening of the immune system, so people with conditions such as HIV are at a higher risk of having this disorder.

What are the symptoms of PML?

Symptoms of PML vary between individuals, depending on where the lesions occur in the central nervous system. The majority of those with PML present some form of brain damage, with may manifest in many different ways, such as mental impairments, vision loss, speech disturbances, facial drooping, issues with coordination and gait, weakness, and the loss of senses. About a third of those with PML experience seizures.

What causes PML?

PML is caused by the JC virus, which infects people during childhood. The virus will remain inactive in the kidneys and lymphoid organs, as it does not cause PML unless the immune system is severely weakened. While the progression of JCV to PML is not exactly known, it seems to be tied to cellular immune dysfunction.

How is PML diagnosed?

An MRI of the brain is the typical method to reach a PML diagnosis. If this imaging test does not work, a brain biopsy is the next option, or a study of the cerebrospinal fluid. Early diagnosis of this condition is critical.

What are the treatments for PML?

There is no cure for JCV, which is the cause of PML. As HIV is a common activator of PML, treatment options vary for those who are HIV positive and those who are HIV negative. HAART is the best option for those who do have HIV, and the removal of any cause of immunosuppression is the best form of treatment for those without HIV.