What Should You Know About Tysabri and Progressive Multifocal Leukoencephalopathy?

Latest update (2026-07)

Tysabri (natalizumab) PML injury claims continue to be evaluated based on individual monitoring and diagnosis records. [source]

From General Health Information to Targeted Risk Awareness

If you or a loved one takes Tysabri, you may be concerned about the risk of progressive multifocal leukoencephalopathy (PML), a serious brain infection. Decades of pharmacovigilance and clinical research have established a clear understanding of this association, guiding monitoring protocols for early detection. This page covers the essential facts about Tysabri-associated PML, including who is at risk, what symptoms to watch for, and how regular surveillance can help manage the risk.

Medical Background: PML and Tysabri

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 Michigan who have developed PML after Tysabri exposure, understanding the medical evidence linking the drug to this harm, as well as the legal time limits for filing a claim, is essential. Progressive multifocal leukoencephalopathy is a viral infection of the brain that typically occurs only in immunocompromised individuals. The infection is caused by the JC virus and usually leads to death or severe disability (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c5fdde91-1989-4dd2-9129-4f3323ea2962). Tysabri increases the risk of PML, as stated in the drug's boxed warning (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c5fdde91-1989-4dd2-9129-4f3323ea2962). Three specific 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). These factors should be considered when initiating and continuing treatment (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c5fdde91-1989-4dd2-9129-4f3323ea2962). The clinical presentation of PML can include progressive neurological deficits such as weakness, vision changes, cognitive decline, and coordination problems. Diagnosis typically involves MRI imaging and detection of JC virus DNA in cerebrospinal fluid. Because PML can be rapidly progressive, the prescribing information mandates that healthcare professionals monitor patients for any new sign or symptom suggestive of PML and withhold Tysabri immediately at the first such sign (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c5fdde91-1989-4dd2-9129-4f3323ea2962). Tysabri is available only through a restricted distribution program called the TOUCH Prescribing Program, which requires regular evaluations and reporting of PML cases (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c5fdde91-1989-4dd2-9129-4f3323ea2962).

Mechanistic Pathways and Adequacy of Warnings

The mechanistic link between Tysabri and PML involves the drug's action as an alpha-4 integrin antagonist. Tysabri blocks the adhesion of immune cells to the blood-brain barrier, reducing their migration into the central nervous system. While this effect is therapeutic for multiple sclerosis, it also impairs immune surveillance against JC virus, allowing the virus to reactivate and cause PML in susceptible individuals. The risk is highest in patients who are anti-JCV antibody positive, indicating prior exposure to the virus, and increases with cumulative treatment duration. The prescribing information for Tysabri includes a boxed warning that clearly states the increased risk of PML and the need for monitoring. However, the adequacy of these warnings in practice has been subject to legal scrutiny. Some patients and their families have argued that the risks were not sufficiently communicated, particularly regarding the magnitude of risk over time and the need for early detection. The TOUCH program is designed to mitigate risk through regular assessments, but cases of PML have still occurred, leading to settlements and litigation.

Settlement-Related Considerations and Statute of Limitations in Michigan

For patients in Michigan who have developed PML after Tysabri use, settlement considerations may include compensation for medical expenses, lost income, pain and suffering, and long-term care needs. The timeline between Tysabri exposure and documented harm is critical. PML typically develops after months to years of treatment, with the highest risk after two years. This latency period can affect the statute of limitations, which in Michigan is generally three years from the date of injury or from when the injury was discovered or should have been discovered. However, the specific facts of each case, including when PML was diagnosed and when the link to Tysabri was recognized, can influence the applicable deadline. Michigan's statute of limitations for personal injury claims, including those related to pharmaceutical products, is generally three years. For wrongful death claims, the limit is also three years from the date of death. The clock typically starts when the plaintiff discovers or reasonably should have discovered the injury and its cause. Given that PML symptoms may be subtle initially and diagnosis can be delayed, patients and their families should consult with a legal professional promptly to determine the applicable deadline in their specific situation. Failure to file within the statute of limitations can bar recovery.

Important Notice

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.

Frequently Asked Questions

What is the statute of limitations for Tysabri-related PML claims in Michigan?

In Michigan, the statute of limitations for personal injury claims, including those related to Tysabri and PML, is generally three years from the date of injury or from when the injury was discovered or should have been discovered. For wrongful death claims, the limit is also three years from the date of death. Because PML symptoms may develop gradually, it is crucial to consult an attorney promptly to determine the applicable deadline.

What are the risk factors for developing PML while on Tysabri?

Three specific 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). These factors should be considered when initiating and continuing treatment.

Does submitting information create an attorney-client relationship?

No. Submission requests an initial records screening only and does not create an attorney-client relationship.

Information Registry: individuals with documented Tysabri exposure and a confirmed Progressive Multifocal Leukoencephalopathy diagnosis may request an independent eligibility review. [Begin Assessment]

References

Tysabri Prescribing Information (DailyMed)

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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.