After taking a fresh look at the data from two previous genome-wide scans for MS-related gene variations, the International MS Genetics Consortium (IMSGC) concluded that MS risk is governed by a cumulative effect of dozens of allelic variants throughout the genome, probably involving as many as 100 genes (N Engl J Med. 2007
; 357(9):851-862; N Engl J Med. 2010
; Apr 9;86(4):621-5. To see the full collection of published genome-wide MS studies, go to www.msgene.org
The role of genetics in MS
As the role of genetics in MS continues to be explored, the following statements can be used to help frame conversations with patients about MS risk (Compston & Coles, 2008):
The risk of developing MS in the general population is approximately 0.1%.
The risk for a child with one parent who has MS is approximately 2%.
The risk for a child with two parents who have MS is approximately 12.2% (Ebers et al, 2000).
The risk for a dizygotic twin and other siblings is approximately 5%.
The risk for monozygotic twins is approximately 25% (Willer et al, 2003).
The risk for second-degree and third-degree relatives is approximately 1%.
Genetic differences between African-Americans and Northern Europeans with MS
Research has demonstrated that MS occurs in most ethnic groups, including African-Americans, Asians and Hispanics/Latinos. Susceptibility rates vary among these groups, with recent findings suggesting that African American women have a higher than previously reported risk of developing MS.
In 2013, a nationwide team of researchers reported the largest genetic study of people with MS of non-European ancestry. Investigators obtained DNA samples from 1,162 African-Americans with MS and 2,092 African-Americans without MS, as well as 577 white Americans with MS and 461 white Americans without MS. The team looked for similarities and differences in 128 gene variants that have been associated with MS. They confirmed associations of key immune-response genes (HLA) with MS among African Americans. However, among 73 non-HLA genes that were associated with MS among white Americans, only 8 were associated with MS among African Americans.
The authors concluded that MS genetic risk in African Americans only partially overlaps with that of Europeans and could explain the difference of MS prevalence between populations.
Conversations about the genetic contribution to MS risk should include mention of the complex interaction with environmental factors that appears to exist.