Multiple sclerosis

Multiple sclerosis (MS) is a non-contagious chronic disease of the brain and spinal cord characterized by a variety of neurologic symptoms caused by demyelination of neurons. Multiple sclerosis results from attack by a patient's own immune system on their central nervous system and is thus categorized as an autoimmune disease.

Epidemiology

In northern Europe, continental North America, and Australasia, about one of every 1000 citizens suffers from multiple sclerosis, whereas in the Arabian peninsula, Asia, and continental South America, the frequency is much lower. In Sub-Saharan Africa, MS is extremely rare. With important exceptions, there is a North-South gradient in the Northern hemisphere and a South-North gradient in the Southern hemisphere, with very low frequencies near the equator. Climate, diet, geomagnetism, toxins, sunlight, genetic factors, and infectious diseases have been discussed as possible reasons for these regional differences. It has been postulated that an environmental factor during childhood might play an important role for the development of MS later in life. This was based on several studies in migrants demonstrating that if migration occurs before the age of 15, the migrant acquires his new region's susceptibility to MS. If migration takes place after 15, the migrant keeps the susceptibility of his home country.

Related Topics:
Europe - North America - Australasia - Arabian peninsula - Asia - South America - Sub-Saharan Africa - Climate - Diet - Geomagnetism - Toxin - Sunlight - Genetic - Infectious disease - Migration

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MS occurs mainly in Caucasians. It is 20-fold lower in the Inuit people of Canada than in other Canadians living in the same region. It is also rare in the Native American tribes of North America, the Australian Aborigine and the Maori of New Zealand. These few examples point out that the genetic background plays an important role in the development of MS (see below).

Related Topics:
Caucasians - Inuit - Canada - Native American - North America - Australian Aborigine - Maori - New Zealand

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As observed in many autoimmune disorders, MS is more common in females than males; the mean sex ratio is about two females for every male. In children, who rarely develop MS, the sex ratio may reach three females for each male, whereas MS occurring in the fifth decade more commonly affects males. Onset of symptoms usually occurs between 20 to 40 years of age, rarely below 15 or above 60, although both are possible.

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MS is not strictly a hereditary disease. However, MS is a disease influenced by a variety of factors, one of which is the genetic background of an individual. There is no single gene known to be responsible for MS, though a few genes have been demonstrated to increase the risk of development. Although these genes are of scientific interest and continue to play a part in research, they are not enough to diagnose an individual with MS.

Related Topics:
Hereditary - Gene

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Overall, on average one of every 25 siblings of an individual with MS will also be afflicted. Up to every second identical twin of a MS-affected person will develop MS, but only one of 20 fraternal twins. If one parent is affected by MS, each child has a risk of only about 1 in 40 to develop MS later in life.

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