If you or a loved one is taking Tysabri, you may be concerned about the risk of Progressive Multifocal Leukoencephalopathy (PML) and what monitoring can reveal. This concern builds on decades of pharmacovigilance research that has established PML as a rare but serious complication of certain immunosuppressive therapies. This page reviews the types of evidence used to assess PML risk, what monitoring tests can and cannot detect, and how to interpret your results.
Tysabri (natalizumab) is a biologic therapy approved as monotherapy for relapsing forms of multiple sclerosis and for Crohn's disease. Its use carries a well-documented risk of progressive multifocal leukoencephalopathy (PML), a severe opportunistic brain infection caused by the JC virus. For patients in Washington who have developed PML after Tysabri exposure, understanding the medical evidence and legal timeframes is critical. PML is an infection of the brain's white matter that typically leads to death or severe disability (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c5fdde91-1989-4dd2-9129-4f3323ea2962). The condition arises when the JC virus, which is normally dormant, becomes active in immunocompromised individuals. Tysabri increases PML risk by altering immune surveillance in the central nervous system. Three primary risk factors have been identified: the presence of anti-JCV antibodies, longer treatment duration (especially beyond two years), and prior use of immunosuppressants (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c5fdde91-1989-4dd2-9129-4f3323ea2962). Patients who are anti-JCV antibody positive face a higher risk, and the combination of these factors should be weighed against expected benefits when initiating or continuing therapy (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c5fdde91-1989-4dd2-9129-4f3323ea2962). Clinical presentation of PML can include progressive weakness, visual changes, cognitive decline, and coordination difficulties. Diagnosis typically involves MRI imaging and detection of JC virus DNA in cerebrospinal fluid. Because PML often leads to irreversible neurological damage, early recognition is essential. The prescribing information mandates that healthcare professionals monitor patients for any new signs or symptoms suggestive of PML and withhold Tysabri immediately at the first indication (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c5fdde91-1989-4dd2-9129-4f3323ea2962).
The U.S. Food and Drug Administration has assigned Tysabri a boxed warning, the strongest safety alert, explicitly stating that the drug increases PML risk (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c5fdde91-1989-4dd2-9129-4f3323ea2962). The warning emphasizes that PML usually leads to death or severe disability. To mitigate risk, Tysabri is available only through a restricted distribution program called the TOUCH Prescribing Program (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c5fdde91-1989-4dd2-9129-4f3323ea2962). Under this program, patients must read a Medication Guide, understand the risks, and sign an enrollment form. Pharmacies and infusion centers must be specially certified to dispense or infuse the drug (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c5fdde91-1989-4dd2-9129-4f3323ea2962). Despite these warnings, questions about the adequacy of risk communication have arisen in legal contexts. Some patients may not have received clear information about PML risk factors or the importance of early symptom reporting. The boxed warning explicitly states that healthcare professionals should monitor patients and withhold Tysabri at the first sign of PML (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c5fdde91-1989-4dd2-9129-4f3323ea2962). However, delays in diagnosis can occur if symptoms are misinterpreted or if monitoring protocols are not followed.
For patients in Washington who have developed PML after Tysabri use, legal claims may involve allegations that the manufacturer failed to adequately warn about PML risks or that the drug was defectively designed. Settlement considerations often depend on the severity of harm, the presence of identifiable risk factors, and the timeline between exposure and documented harm. The statute of limitations for personal injury claims in Washington is generally three years from the date the injury was discovered or reasonably should have been discovered. For PML, this discovery date may be when a patient receives a definitive diagnosis or when symptoms become clearly attributable to the drug. Because PML can develop months to years after starting Tysabri, the clock may start later than the initial exposure. However, patients should not delay seeking legal advice, as courts may apply strict deadlines. Evidence of harm includes medical records documenting PML diagnosis, MRI findings, JC virus testing, and treatment history. The duration of Tysabri therapy is a key factor, as risk increases with longer use, especially beyond two years (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c5fdde91-1989-4dd2-9129-4f3323ea2962). Prior immunosuppressant use also elevates risk and may strengthen a claim that warnings were insufficient.
Tysabri-associated PML is a devastating condition with well-established risk factors and regulatory warnings. Patients in Washington who have suffered this harm should be aware of the three-year statute of limitations from discovery of injury. Medical evidence, including antibody status, treatment duration, and prior immunosuppression, is central to evaluating both clinical risk and legal claims. Prompt action is essential to preserve legal rights.
This page is for educational and informational purposes only. It does not provide medical diagnosis, treatment, or legal advice. Consult licensed clinicians and qualified attorneys for case-specific decisions.
In Washington, the statute of limitations for personal injury claims is generally three years from the date the injury was discovered or reasonably should have been discovered. For PML, this may be when a definitive diagnosis is made or when symptoms become clearly attributable to Tysabri.
The three primary risk factors are: presence of anti-JCV antibodies, longer treatment duration (especially beyond two years), and prior use of immunosuppressants. These factors are detailed in the prescribing information (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c5fdde91-1989-4dd2-9129-4f3323ea2962).
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This page is for educational and informational purposes only and is not medical or legal advice. Consult a licensed professional for case-specific guidance.
Individuals with documented Tysabri exposure and a related diagnosis may request an independent, no-cost eligibility review.