New Antibody Test Shown to Indicate PML Risk

If you test positive for having antibodies to the JC virus (JCV), you have an increased risk of getting progressive multifocal leukoencephalopathy (PML), according to a Food and Drug Administration (FDA) Safety Communication released Jan. 20, 2012.

PML is a rare serious infection of the brain that occurs in patients treated with Tysabri® (natalizumab) for multiple sclerosis (MS) or Crohn’s disease.  Patients and their doctors should discuss the risks and benefits of taking Tysabri® for MS or Crohn’s disease.

There are three risk factors for PML. A patient having all three has of getting PML of 11 in 1,000. The three risk factors are:

  • The presence of anti-JCV antibodies
  • Long-time treatment with Tysabri®, in particular longer than two years
  • Prior treatment with an immunosuppressant medication

Patients should talk with their physicians if they develop symptoms that characterize PML. Symptoms vary and become worse over a period of days or weeks. These symptoms include progressive weakness on one side of the body, clumsiness, problems seeing, changes in thinking, memory and orientation that end in confusion and personality changes.

If you test positive for the presence of anti-JCV antibodies, you have been exposed to JCV in the past.

The drug label accompanying a Tysabri® prescription reflects this new information.

The nerve fibers of patients with PML have been damaged. It is a rare disease that does not harm people with normal-functioning immune systems. People with weakened immune systems are more susceptible to the disorder, in particular people who are immunodeficient due to having HIV infection (the human immunodeficiency virus); having leukemia or lymphoma; taking Tysabri®.

It still is possible to be at risk for developing PML, even if you test negative for anti-JCV antibodies. This is because it is possible to get a new JCV infection or for test results to be inaccurate.


For more information, contact a PML lawyer today.

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