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| {{Amyotrophic lateral sclerosis}}
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| {{CMG}}
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| {{Amyotrophic lateral sclerosis}} | | {{Amyotrophic lateral sclerosis}} |
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| [[Category: (name of the system)]] | | [[Category: (name of the system)]] |
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| ==Historical Perspective==
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| The word ''amyotrophic'' is present Greek in origin. ''A'' means no or negative, ''myo'' refers to [[muscle]], and ''trophic'' means nourishment. When put together it means "no-muscle-nourishment." ''[[Anatomical terms of location|Lateral]]'' identifies the areas of the [[spinal cord]] where portions of the nerve cells that signal and control the muscles are located. As this area degenerates it leads to scarring or hardening ([[sclerosis]]) in the region. <ref>[http://www.alsa.org/als/what.cfm What is ALS - The ALS Association] Retrieved October 24, 2006</ref>
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| ==Classification==
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| ALS is classified into three general groups, '''familial ALS''', '''sporadic ALS''' and '''Guamanian ALS'''.
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| ==Pathophysiology==
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| The cause of ALS is not known. An important step toward answering that question came in 1993 when scientists discovered that mutations in the gene that produces the Cu/Zn [[superoxide dismutase]] (SOD1) enzyme were associated with some cases (approximately 20%) of familial ALS. This enzyme is a powerful antioxidant that protects the body from damage caused by [[superoxide]], a toxic free radical. [[Free radicals]] are highly reactive molecules produced by cells during normal [[metabolism]]. Free radicals can accumulate and cause damage to [[DNA]] and proteins within cells. Although it is not yet clear how the SOD1 gene mutation leads to motor neuron degeneration, researchers have theorized that an accumulation of free radicals may result from the faulty functioning of this gene. Current research, however, indicates that motor neuron death is not likely a result of lost or compromised dismutase activity, suggesting mutant SOD1 induces toxicity in some other way (a gain of function).<ref name="mSOD1 gene deletion does not cause MND">{{cite journal |author=Reaume A, Elliott J, Hoffman E, Kowall N, Ferrante R, Siwek D, Wilcox H, Flood D, Beal M, Brown R, Scott R, Snider W |title=Motor neurons in Cu/Zn superoxide dismutase-deficient mice develop normally but exhibit enhanced cell death after axonal injury |journal=Nat Genet |volume=13 |issue=1 |pages=43-7 |year=1996 |id=PMID 8673102}}</ref><ref name="wtSOD1 elevatation/elimination do not change disease course">{{cite journal |author=Bruijn L, Houseweart M, Kato S, Anderson K, Anderson S, Ohama E, Reaume A, Scott R, Cleveland D |title=Aggregation and motor neuron toxicity of an ALS-linked SOD1 mutant independent from wild-type SOD1 |journal=Science |volume=281 |issue=5384 |pages=1851-4 |year=1998 |id=PMID 9743498}}</ref>
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| ==Causes==
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| 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. 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.
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| ==Epidemiology and Demographics==
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| ALS is one of the most common neuromuscular diseases worldwide, and people of all races and ethnic backgrounds are affected.
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| ==Risk Factors==
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| Risk factors for the development of ALS include; possessing an inherited mutation in chromosome 21, being a child of someone diagnosed with familial ALS, prolonged exposure to a dietary neurotoxin found in the seed of the cycad plant, and being a military veteran.
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| ==References==
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| {{reflist|2}}
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| [[Category:Motor neuron disease]]
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| [[Category:Neurology]]
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| [[Category:Disease]]
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| {{WH}}
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| {{WS}}
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