Genetic
· Experts believe that if you are related to someone with MS, you have an elevated risk of developing the disease. Studies have shown the offspring of MS sufferers to be forty times more likely to develop the disease than those of healthy parents. This still represents quite a low incidence however with only 2% of “at risk” offspring going on to develop MS.
· Genetic variations in the Human Leukocyte Antigen (HLA) area on Chromosome 6 have been found to correlate with an increased incidence of MS. Where some HLA loci have been suggested to cause MS, other genes in this region have been seen to have preventative effects. It is believe several different genes have a role in the disease of only 35% of monozygotic twins will both be sufferers when one of them develops the disease. This figure is reduced further to 5% when referring to normal siblings.
· Globally, the highest incidences of MS appear in countries furthest from the equator with European countries, particularly Scotland, and Canada having some of the highest. This has led to speculation into whether the migration of Vikings has caused the distribution. Studies finding the incidence of MS in Scotland to be double that in England certainly support the theory that Viking genetics have dictated the disease’s spread.
The purely genetics model has its limitations. Different races within countries, such as the Inuit’s of Canada, seem to have a much smaller predisposition to MS. By observing migrants, it has been seen that those who move early in life adopt the incidences of the country they’re moving to. This points towards the disease’s environmental factor.