introduction
Multiple sclerosis (MS) has the characteristics of an autoimmune disease and affects the central nervous system (the brain and spinal cord). MS causes inflammation within the brain and spinal cord which destroys myelin, a protective layer that covers the nerves. This leaves multiple areas of scar tissue (sclerosis) and leads to slower or blocked nerve impulses, resulting in the signs and symptoms of MS. Repeated episodes of inflammation (called flare-ups) can occur in any area of the brain and spinal cord. Symptoms depend upon which nerves are affected, but may include changes in the senses, balance, muscle strength and thinking. Diagnosis of MS requires clinical evidence of lesions and the exclusion of inflammatory, structural, or hereditary conditions that might result in similar symptoms. The course of the disease varies from minor disability to wheelchair dependency within a few years after disease onset.MS is the most common cause of neurological disability in young adults. Approximately 90% of affected individuals are diagnosed before the age of 60 and most of them are between 20 and 40 years of age. Less than 5% are diagnosed before puberty. The prevalence varies with geography, ethnicity and gender, and is highest in white populations living in temperate regions. In Europe and North America, the prevalence is 1 in 800 (1 in 1200 males and 1 in 600 females), with an annual incidence of 2 to 10 per 100,000 individuals.
MS is uncommon in Japan, China, and South America. It is practically unknown among the indigenous people of equatorial Africa, native Inuits in Alaska, and Lapps in Scandinavia. Based on a 2007 study of the UK population, 5.3 per 1,000 women and 2.3 per 1,000 men are expected to receive a diagnosis of MS during their lifetime.
The risk of developing MS is in part genetically determined. Three genetic variants have been found to increase the risk of developing MS. They are located in or near the HLA-DRA gene on chromosome 6, the IL-2Ra gene on chromosome 10, and the IL-7R gene on chromosome 5.
The deCODEme Genetic Scan identifies the three genetic variants listed above in customers of European descent and provides interpretation of their associated risk for the development of MS. Currently no data are available for people of other ethnicities for the variants listed above.
risk factors
Researchers have not yet found the exact cause of MS, but they have identified the following factors that may increase the risk for MS:- Ethnicity: MS is more common in people of Northern European descent.
- Environmental factors: Viruses and bacteria have been suspected of contributing to the development of MS. Patients with MS typically have a higher number of immune cells than a healthy person, which suggests that an immune reaction to a viral or bacterial infection might play a role.
- Geographical factors: MS is more common in countries with temperate climates, including Europe, southern Canada, northern United States, and southeastern Australia and New Zealand. The reason for this is unknown, but geographic studies suggest that it may be due to environmental factors, genetic factors, or both.
- Genetics: Although the risk of developing MS in children whose parents are affected by MS is less than 5% over their lifetime, genetic research supports the hypothesis that the tendency to develop MS is inherited. However, whether the disease develops depends on exposure to environmental triggers.
more information
You can find out more information about MS by talking with your doctor and visiting these Web sites: MedlinePlus Medical EncyclopediaThe National Institute of Neurological Disorders and Stroke
National Multiple Sclerosis Society
The Multiple Sclerosis Association of America