Risk of progressive multifocal leukoencephalopathy in patients with multiple sclerosis

Introduction: Multiple sclerosis (MS) is an autoimmune disorder that is characterized by inflammatory processes that lead to the destruction of myelin. Recently, several medications for MS that possess immune suppressing characteristics have been developed. As a consequence, cases of progressive multifocal leukoencephalopathy (PML) have been identified in MS patients. PML is potentially fatal, and specific strategies to minimize risk must be undertaken during therapy. Areas covered: A Medline search was performed to gather information about medications used to treat MS to assess the risk of PML with each. Specific risk factors for infection development are discussed and monitoring approaches are outlined. Expert opinion: Several medications have been associated with PML in MS patients, including natalizumab, fingolimod and dimethyl fumarate. Alemtuzumab and rituximab have been linked to cases of PML in other disease states. Consideration must be given to balancing efficacy with the potential for serious side effects, including PML. The severity of MS presentation may justify the use of a higher-risk medication at the outset. Increased diligence in obtaining MRIs and antibody status is essential as data demonstrate early identification of PML results in better outcomes. Lymphopenia and antibody index also appear to be reasonable factors to consider when choosing therapy.