Causes of PML

Progressive multifocal leukoencephalopathy (PML) is a life-threatening disease caused by a virus called the John Cunningham virus (JCV). The virus was identified in 1967 as the cause of the disease and was named in 1971when it was isolated from the brain of a patient named John Cunningham. The virus is very common and exists in more than 70 percent of the population.

JCV remains harmless and latent in the kidneys and gastrointestinal tract until it is activated when the immune system becomes compromised. The virus then travels through the circulatory system to the brain and spinal cord where it destroys the myelin, an insulating layer that protects the nerves. When the myelin is damaged, nerves cannot transmit messages from one nerve cell to another.

Diagnosis of PML is made by checking the cerebrospinal fluid for the presence of JCV. Magnetic resonance imaging can show brain lesions of PML, but the definitive diagnosis is to find the JCV in the cerebrospinal fluid.

Symptoms of PML

There is no known treatment or cure for PML. Symptoms, which worsen over time, include:

  • Headaches
  • Progressive weakness of the arms and legs
  • Vision problems
  • Clumsiness and lack of coordination
  • Memory loss
  • Aphasia (loss of ability to speak, listen, read and write)

PML occurs in patients with deficient immune systems, mainly in persons infected with HIV. HIV infection accounts for 85 percent of all persons who have PML. PML is more likely to occur in those HIV patients whose immune systems are more greatly depressed. The PML virus also is found in:

  • Organ transplant patients on immunosuppressive drugs (PML is a rare occurrence in these patients)
  • People with AIDS
  • Patients with compromised immune systems such as those with systemic lupus erythematosus
  • Patients with certain cancers, including Hodgkin's disease, lymphoma, and sarcoidosis
  • Gilenya, a multiple sclerosis drug, may be linked to PML
  • Patients who have chronic corticosteroid or immunosuppressive therapy, including the drug Raptiva®.

Raptiva was approved in 2003 to treat adults with moderate to severe plaque psoriasis. Its manufacturer, San Francisco-based Genentech, withdrew the drug from the market in April 2009, because it was found to be causing PML in some patients. At the time it was pulled from the market approximately 46,000 patients worldwide had been treated with the drug. Genentech made $108 million from selling Raptiva in 2008.

If you developed progressive multifocal leukoencephalopathy and believe it's drug-related, contact our PML attorneys today.

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