Genetics and Multiple Sclerosis: What Should You Know?
As a person with MS, you have probably wondered about the genetics involved with the disease. Will it be passed down to your children? What is the likelihood? In this week's segment from the Consortium of Multiple Sclerosis Centers (CMSC), we want to talk about exactly that. In their recent paper, "The Basics of Genetics in Multiple Sclerosis," two MS nurses write about the risks and details:
"The risk of developing MS in people who have no relatives with MS is about 1 in 1,000. Eighty percent (80%) of people who develop MS have no relatives with MS, and 20% have at least one affected relative with the disease. The risk of MS in the siblings of a person with MS is significantly higher. A measure of the size of the genetic component of disease susceptibility is the sibling risk, which is defined as the ratio of the disease risk in a sibling of an affected individual to the general population. The sibling risk for MS may range from 1 in 20 to 1 in 50. As one moves from siblings to first and third cousins, the risk decreases. However, the first, second, and third-degree relatives of people with MS are more likely to have the disease than the general population (Dyment, Ebers, & Sadovnick, 2004).
Adoptive relatives, although raised from infancy with the MS patient, have the same susceptibility to MS as the general population. This evidence substantiates the fact that familial aggregation of MS is related to genetic sharing rather than to a shared environment (Ebers et al., 1995). The half-sibling and full sibling studies showed a 2.35% for MS in siblings with a shared mother who had MS, and 1.31% for a shared father who had MS, indicating a maternal effect. The risk of transferring MS from mother to siblings was higher (Dyment, Ebers, & Sadovnick, 2004; Ebers, 1996).
Identical monozygotic twins are more often concordant for MS than dizygotic twins (26% versus 2.4%), which correlate with a genetic component. However, following monozygotic twins past age 50, and using clinical findings and MRI data, less than 50% were concordant, suggesting a role for environmental factors (Ebers et al., 1986; Hupperts et al., 2001). High infant contact in the first six years of life was associated with a reduced risk of MS. High infant contact was also associated with a reduced risk of elevated Epstein Barr Virus antibodies or infectious mononucleosis among healthy controls.
This emphasizes the fact that the association between infant contact and MS relates to early infection exposure and the immune response to infections. In addition, increasing numbers of younger siblings was strongly associated with a reduced risk of MS (Ponsonby et al., 2005). This study strengthens the belief that MS is mediated by self-reactive T cells that may be induced by viral or other environmental factors."
Want to learn more about the role of genetics in your condition? Read more from the CMSC paper here.