While research suggests that MS is not directly inherited, genetics appear to play a role in predisposing or increasing a person’s chances for developing MS. Just as our DNA, which we inherit from our parents, determines whether we have blue or brown eyes or whether we are tall or short, our genes influence the way our immune systems develop and work.
Experts believe that people who develop MS inherit something in their immune system that makes them more reactive to whatever it is that causes the immune system to attack myelin surrounding nerves in the CNS.
It is likely that a still undiscovered environmental agent or agents (many believe it’s viral or bacterial) triggers the autoimmune response that leads to MS in a person who has an inherited, or genetic, susceptibility in their immune system.
What do genetic studies tell us?
It is believed that individuals whose ancestors are from northern or central Europe have a genetic predisposition to MS. Studies have even identified specific types of genes that are more common among groups of people in which MS occurs more frequently.
Evidence from twin studies has shown us that MS is not a purely inherited disease. If it were an inherited disease, you would expect that identical twins (or monozygotic twins) who share all the same genes would both develop MS. However, only a quarter to a third of monozygotic twins both develop MS. This suggests that some environmental agent must trigger the disease in people who are genetically susceptible.
Genetic studies using advanced computer technology to scan the entire genome have begun to identify genetic abnormalities that may increase a person’s susceptibility for MS. Results from these studies may eventually allow us to predict who is at greatest risk for developing MS.
If I have MS, are my children likely to get it?
We know that if you have a parent or sibling (a first-degree relative) who has MS it increases your likelihood of developing MS considerably.
For instance, in the general population there is a 1 in 750 chance for developing MS (rather 1 in 750 people in the general population develops MS). However, if a person has a first-degree relative with the disease, the risk for MS increases to around 2 to 5 in 100.
Despite this increased risk, even with a family history of MS, the chance of developing the disease is still relatively small. However, the risk does rise again in families which have more than one member living with MS.