MS Drug Linked to Death from Serious Brain Infection

The FDA is warning that a patient with multiple sclerosis (MS) who was being treated with Tecfidera (dimethyl fumarate) developed a rare and serious brain infection called progressive multifocal leukoencephalopathy (PML), and later died. The patient who died was not taking any other drugs that affect the immune system or drugs that are thought to be associated with PML. As a result, information describing this case of PML is being added to the Tecfidera drug label.


Tecfidera is a drug used to treat relapsing forms of MS, a brain and spinal cord disease in which patients experience multiple episodes of weakness, numbness, and other nervous system signs and symptoms that partially or completely resolve over weeks or months. Patients may develop persistent symptoms and disability over time.


PML is a rare and serious brain infection caused by the John Cunningham (JC) virus. The JC virus is a common virus that is harmless in most people but can cause PML in some patients who have weakened immune systems.


The drug manufacturer, Biogen Idec, notified the FDA when the MS patient died after developing PML. The patient had taken Tecfidera for more than four years. Prior to developing PML, the patient had a very low number of lymphocytes, a type of white blood cell, in her blood. Reduced lymphocyte counts can weaken the immune system, which increases the risk for PML. It is unknown whether the low lymphocyte count contributed to the development of PML in this patient, or if low lymphocyte counts are a risk factor for PML development in Tecfidera-treated patients.


Symptoms of PML are diverse, progress over days to weeks, and include the following:

  • progressive weakness on one side of the body or clumsiness of limbs;
  • disturbance of vision; and
  • changes in thinking, memory and orientation, leading to confusion and personality changes.


The progression of deficits can lead to severe disability or death.


Approximately 4,000 patients have taken Tecfidera in MS clinical trials, including 1,000 patients treated for at least four years. Biogen reports that more than 100,000 patients with MS worldwide have taken Tecfidera since the FDA approved it in 2013.


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See also Medical Law Perspectives, May 2013 Report: Drugs, Dosage, and Damage: Physician Liability for Prescribing or Administering Medication