2 December 2008, 2:24 am
ALS is one of the most common neuromuscular diseases worldwide, and people of all races and ethnic backgrounds are affected. One to 2 people per 100,000 develop ALS each year.[2] ALS most commonly strikes people between 40 and 60 years of age, but younger and older people can also develop the disease. Men are affected slightly more often than women. "Familial ALS" accounts for approximately 5%–10% of all ALS cases and is caused by genetic factors. Of these, approximately 1 in 10 are linked to a mutation in copper/zinc superoxide dismutase (SOD1), an enzyme responsible for scavenging free radicals. An antisense drug trial is underway using a small interfering RNA molecule (siRNA) that inhibits the production of this mutant SOD1 protein.[3] Although the incidence of ALS is thought to be regionally uniform, there are three regions in the West Pacific where there has in the past been an elevated occurrence of ALS. This seems to be declining in recent decades. The largest is the area of Guam inhabited by the Chamorro people, who have historically had a high incidence (as much as 143 cases per 100,000 people per year) of a condition called Lytico-Bodig disease which is a combination of ALS, Parkinsonism, and dementia.[4] Two more areas of increased incidence are the Kii peninsula of Japan and West Papua.[5][6] Although there have been reports of several "clusters" including three American football players from the San Francisco 49ers, more than fifty soccer players in Italy [7], three soccer-playing friends in the south of England,[8] and reports of conjugal (husband and wife) cases in the south of France,[9][10][11][12][13] these are statistically plausible chance events. Although many authors consider ALS to be caused by a combination of genetic and environmental risk factors, so far the latter have not been firmly identified, other than a higher risk with increasing age. Cause and risk factors Scientists have not found a definitive cause for ALS and the onset of the disease has been linked to several factors, including: a virus; exposure to neurotoxins or heavy metals; DNA defects; immune system abnormalities; and enzyme abnormalities. Surgeries involving the spinal cord have also been thought to play a role in the onset of ALS due to the disruption of nerve fibers. There is a known hereditary factor in familial ALS (FALS); however, there is no known hereditary component in the 90-95% cases diagnosed as sporadic ALS. An inherited genetic defect on chromosome 21 is associated with approximately 20% of familial cases of ALS.[14][15] This mutation is believed to be autosomal dominant. The children of those diagnosed with familial ALS have a higher risk factor for developing the disease; however, those who have close family members diagnosed with sporadic ALS have no greater a risk factor than the general population [1]. Some causative factors have been suggested for the increased incidence in the western Pacific. Prolonged exposure to a dietary neurotoxin called BMAA is one suspected risk factor in Guam; the neurotoxin is a compound found in the seed of the cycad Cycas circinalis,[16] a tropical plant found in Guam, which was used in the human food supply during the 1950s and early 1960s. The very high incidence of the disease among Italian soccer players (more than five times higher than normally expected) has raised the concern of a possible link between the disease and the use of pesticides on the soccer fields.[17] [18] According to the ALS Association, military veterans are at an increased risk of contracting ALS. In its report ALS in the Military,[19] the group pointed to an almost 60% greater chance of the disease in military veterans than the general population. For Gulf War veterans, the chance is seen as twice that of veterans not deployed to the Persian Gulf in a joint study by the Veterans Affairs Administration and the DOD.[20][21] Dietary intake of polyunsaturated fatty acids (PUFA) has been shown in several studies to decrease the risk of developing ALS [22] [23] Symptoms Initial symptoms The onset of ALS may be so subtle that the symptoms are frequently overlooked. The earliest symptoms are obvious weakness and/or muscle atrophy. This is followed by twitching, cramping, or stiffness of affected muscles; muscle weakness affecting an arm or a leg; and/or slurred and nasal speech. The twitching, cramping, etc. associated with ALS is a result of the dying muscle, therefore these symptoms without clinical weakness or atrophy of affected muscle is likely not ALS. The parts of the body affected by early symptoms of ALS depend on which motor neurons in the body are damaged first. About 75% of people experience "limb onset" ALS. In some of these cases, symptoms initially affect one of the legs, and patients experience awkwardness when walking or running or they notice that they are tripping or stumbling more often. Other limb onset patients first see the effects of th dude if yo will just write some cr*ppy things like do your own work or hell that is super easy why cant you just do it yourself... look i admit that i suck at writing paragraphs or summarize things... AINT THAT WHY IM ASKING "YAHOO ANSWERS" people answer not write cr*ppy things and dont even bother answering :| :|... Read More »
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