A review of the etiology of multiple sclerosis.

The geographic distribution of multiple sclerosis and the influence of migration on the risk of contracting it point to an environmental factor as cause of the disease. This environmental factor might be a virus which might produce the demyelination process through an autoimmune reaction against components of the central nervous system. The other possible cause of multiple sclerosis is a genetic susceptibility, inferred from the higher risk for the disease found among relatives of patients with multiple sclerosis and on the association between the disease and some histocompatibility antigens of the HLA system. Both theories seem to be correct, with the environmental factors(s) causing multiple sclerosis only in the presence of a genetic susceptibility.