Hader WJ, Yee IM. The prevalence of familial multiple sclerosis in saskatoon, Saskatchewan. Mult Scler Int. 2014;2014:545080. doi: 10.1155/2014/545080. Epub 2014.
Background. A population-based prevalent cohort of 150 clinical definite multiple sclerosis (MS) cases (102 women; 48 men) ascertained on January 1, 1977, Saskatoon, Saskatchewan, was found to have a familial rate of MS as 17.3%.
Objectives. To determine the occurrence of familial MS cases and the frequency of MS among the biological relatives of the study cohort.
Methods. The search for new familial cases MS affected relatives continued for 35 years until 2012. The natural history of the disease of sporadic cases is compared with that of the familial cases.
Results. Of the 150 unrelated MS patients, 49 cases (32.7%) (36 women and 13 men) were reported of having at least one family member with MS. There were a total of 86 affected relatives, 26 (30.2%) first-degree relatives, 15 (17.4%) second-degree relatives, 20 (23.3%) third-degree relatives, and 25 (29.1%) distant relatives. The average age of MS onset for men with sporadic MS was 33.9 (SD = 10) years and 27.6 (SD = 8.4) years for familial cases and 29.3 (SD = 8.3) years and 26.8 (SD = 8.5) years for women. Conclusion. This 35-year longitudinal natural history study reveals a high frequency of cases with family members developing MS and supports a genetic influence in the aetiology of MS.
Genetic links to disease classify effects of either familial (runs in families) or sporadic (chance occurrence).
Although MS is typically considered sporadic and there is no single MS gene (few genes) that cause MS, yet it is clear that there is familial MS. You just talk to MSers. There are people with parents and aunts and uncles with MS etc. These are more related to you and so are more similar genetically similar to you and further indicates that there is a genetic component to MS. However, just because you have MS genes does not mean you will get MS, indeed identical twin studies indicate that there is a bout a 70-75% chance that you won’t get MS.
In Canada they have been keeping records on MS or years and they have found familial cases where multiple members in a family have MS and conclude that there are genetic causes of MS. Indeed we know the identity of over one hundred genetic variants that increase the risk of MS. In large populations genetic variation is going to be increased compared to small populations.
In this Canadian Study this familial risk was higher than in other studies in different populations