Multiple sclerosis: Epidemiology, genetics, classification, natural history, and clinical outcome measures

The spectrum of MS is broad, with considerable clinical, pathologic⁵² and radiologic heterogeneity. This heterogeneity, along with the chronic nature of the disease, makes it more difficult to identify the epidemiologic and genetic factors that contribute to MS susceptibility and course. Despite these obstacles, the precision of MS classification has improved. Genetic contribution to MS risk has been proved, and at least one substantial contributor, the major histocompatibility complex, has been identified. The natural history of MS has been more accurately characterized. Finally, more objective and reliable quantitative measures of the disease are evolving, among the most important of which are the MR imaging techniques that are the subject of this issue.