Abstract
* A patient contracted progressive multifocal leukoencephalopathy (PML) and died after taking dimethyl fumarate (Tecfidera) to treat relapsing multiple sclerosis.
* Patients who take dimethyl fumarate and develop any new or worsening weakness on one side; trouble using the arms or legs; or changes in thinking, eyesight, strength, or balance should contact their prescriber immediately for evaluation.