Amyotrophic lateral sclerosis classification
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
ALS is classified into three general groups, familial ALS, sporadic ALS and Guamanian ALS.
Classification
- "Familial ALS" accounts for approximately 5%-10% of all ALS cases and is caused by genetic factors. Of these approximately 10% are linked to a mutation in Superoxide dismutase (SOD1), a copper/zinc dependant dismutase that is responsible for scavenging free radicals.
- Most of the remaining 90-95% of cases are classified as "sporadic ALS" and have no known hereditary component.
- A third type, called "Guamanian ALS", represents a small cluster of cases concentrated on the Pacific island of Guam.
Guamanian ALS
There was a high inicidence of this rare form of ALS from the 1940s to the 1960's, and during this thie, the rates of ALS increased by 50 to 100 times of its incidence prior to this time. The incidence of Guamanian ALS has dropped significantly since the 1960's, but during it's peak, it killed more than 10% of the native Chamorro people of Guam.
Parkinson's and Alzheimers Association
Unique to the Guamanian form of ALS, it is associated with the development of cognitive symptoms similar to those seen in Parkinson's disease and Alzheimers dementia. Other forms of ALS tend to only effect the nerves which control the motor function, and do not affect the brain and the mental function.
Non-filtered Drinking Water
Researchers believe that there are algae and bacteria found in large quantities in areas of Guam, that produce powerful neurotoxins during particular times of the year. Prior to the 1960's, the drinking water was not filtered, and therefore people may have consumed high amounts of these toxins and subsequently developed ALS.