Genetics of multiple sclerosis.

The cause of MS is unknown. There is considerable circumstantial evidence that MS is a complex trait, probably autoimmune in nature, and is determined by both genetic and environmental factors. At present, it must be acknowledged, however, that our understanding of the pathogenesis of MS is minimal. Very little is known about the genes determining disease susceptibility and perhaps even less is understood about environmental factors that influence penetrance or the geographic distribution. This lack of knowledge results neither from lack of effort nor from a shortage of fertile imaginations. Almost every imaginable hypothesis has, in the past, found some support. The intractability of the problem could well result from its complexity, because answers to testable hypotheses are commonly negative or ambiguous. Today, the opportunity exists for researchers to provide such answers because of recent major developments. The first development is the recognition that MS research requires a relatively large pool of well-ascertained, carefully diagnosed, and longitudinally well-characterized MS patients. The last two developments are the identification and successful application of statistical and molecular genetic techniques carrying sufficient power to allow the exploration of complex traits such as MS.