Asked by Danette, Orange, California
Is multiple sclerosis genetic or hereditary? If so, what are the statistics (for example 1 in 1,000)?
Dr. Otis Brawley
Chief Medical Officer,
American Cancer Society
Multiple sclerosis is a disease of the nervous system. It involves demyelination, and nerve degeneration. Demyelination is the removal of the covering of the nerve through an inflammatory response. A good analogy is to think of the nerve as an electrical wire running from the brain to the periphery. Like electrical wires, nerves convey electricity from the brain to muscles to cause movement or from sensors through the body to the brain to cause sensations such as pain, heat, cold or sight. Myelin is the covering of a nerve, just as plastic covers an electrical wire. Demylination, the hallmark of MS, is the removal of that covering. It begins with an inflammatory reaction in the affected nerve causing the nerve to dysfunction and ends as that nerve dies. Persons with MS will lose the function that nerve carried out.
People with severe MS will lose the function of a number of nerves over time and can lose a number of body functions and have phantom pains as a result.
There are several types of MS. Most but not all patients who have MS develop it in their mid 20s to late 30s. For unknown reasons, women are disproportionately affected compared with men. There are some data to suggest that patients with other autoimmune disorders such as type 1 diabetes mellitus, autoimmune thyroid disease and lupus are at increased risk of MS. Women tend to get more of these diseases compared with men as well.
We do not know the cause of the immune system turning on the nerve's insulator. Viral infections may cause this. There is some interest in the Epstein-Barr virus, which causes mononucleosis, as a possible cause of MS. There are also interesting studies that suggest that kids who have a lot of exposure to other kids and their viruses before the age of 6 are at lower risk of MS compared with folks who were relatively isolated from other kids as children.
In the United States the prevalence is about 100 cases per 100,000 Americans. This means about a quarter-million Americans have the disease. There is a geographic variation in the disease. MS is of higher prevalence in Europe (including Russia), southern Canada, the northern United States, New Zealand, and southeast Australia. The prevalence is 1.5 to 2 times greater in the northern United States compared with the southern states.
A Danish study does suggest that relatives of MS patients may be as much as seven times more likely to get the disease compared to people with no known relatives with the disease. This may be the result of common genetics. It could also be caused by common environmental exposures. No one knows for sure. At this time there is no known prevention.
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