Multiple Sclerosis After Infectious Mononucleosis

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Abstract
Despite many years of intensive research, the causes of multiple sclerosis (MS) remain unknown. The prevailing view is that MS is an autoimmune disorder that results from various environmental factors acting in a genetically susceptible host.1 Different lines of evidence have implicated infection with the Epstein-Barr virus (EBV) in the development of MS. Investigations have shown that levels of certain EBV antibodies correlate with MS disease activity2,3 and are predictive of MS risk in apparently healthy individuals.4-6 Because more than 90% of healthy adults are infected with EBV, infection alone is clearly insufficient to cause MS. Age at primary infection and the host's immunological response may be modifiers of the EBV-associated risk of MS. Accordingly, infectious mononucleosis, usually caused by EBV infection in adolescence, has been associated with an increased risk of MS in small cohort studies and, less compellingly, in case-control studies.7 However, the association between mononucleosis and the risk of MS remains poorly characterized with respect to sex and age at and time since mononucleosis. Because such information is pertinent to understanding the association, we assessed the risk of MS in a cohort study of patients diagnosed as having mononucleosis.