Is multiple sclerosis inherited? What's the genetic factor?

Multiple sclerosis is a typical complex trait and susceptibility is genetically determined. In the population at large, the chance of developing multiple sclerosis is less than a tenth of one percent. However, if one person in a family has multiple sclerosis, that person's first-degree relatives parents, children, and siblings have a one to three percent chance of getting the disease. For identical twins, the likelihood that the second twin may develop multiple sclerosis if the first twin does is about 30 percent; for fraternal twins (who do not inherit identical gene pools), the likelihood is closer to that for non-twin siblings, or about 4 percent. The fact that the rate for identical twins both developing multiple sclerosis is significantly less than 100 percent suggests that the disease is not entirely genetically controlled. Some (but definitely not all) of this effect may be due to shared exposure to something in the environment, or to the fact that some people with multiple sclerosis lesions remain essentially asymptomatic throughout their lives. In addition, increasing scientific evidence suggests that genetics may play a role in determining a person's susceptibility to multiple sclerosis. Some populations, such as Gypsies, Eskimos, and Bantus, never get multiple sclerosis. Native Indians of North and South America, the Japanese, and other Asian peoples have very low incidence rates. It is unclear whether this is due mostly to genetic or environmental factors.

Although no specific gene for multiple sclerosis has been identified, several researchers have concluded that people with multiple sclerosis inherit certain regions on individual chromosomes more often than people without multiple sclerosis. Researchers are investigating the human leukocyte antigen (HLA) on chromosome 6, since the HLA patterns of multiple sclerosis patients appear to be different from those who do not have multiple sclerosis. Development of multiple sclerosis is likely to be influenced by the interactions of a number of genes, each of which (individually) has only a modest effect. Additional studies are needed to specifically pinpoint which genes are involved, determine their function, and learn how each gene's interactions with other genes and with the environment make an individual susceptible to multiple sclerosis. In addition to leading to better ways to diagnose multiple sclerosis, such studies should yield clues to the underlying causes of multiple sclerosis and, eventually, to better treatments or a way to prevent the disease.

More information on multiple sclerosis