Question: What causes Amyotrophic lateral sclerosis ?
Answer: What causes amyotrophic lateral sclerosis? In approximately 90-95% of cases the cause of amyotrophic lateral sclerosis (ALS) is unknown and is sporadic (occurring in individuals with no history of the condition in the family). The remaining 5-10% of cases are genetic (familial), often occurring in individuals with a family history of the condition. Mutations in any of several genes, including the C9orf72, SOD1, TARDBP, FUS, ANG, ALS2, SETX, and VAPB genes, can cause familial ALS and may contribute to the development of sporadic ALS. About 60% of individuals with familial ALS have an identifiable genetic mutation; the genetic cause in the remaining cases is unknown. The genes associated with ALS appear to play a role in how neurons function or are involved in regulating the production of various proteins. Over the years, various types of environmental exposures have been proposed as possible contributors to the cause of ALS, including mercury, manganese, products used in farming (fertilizers, insecticides, herbicides), and physical and dietary factors. Exposures have been suggested as a possible explanation for the increased incidence of ALS in Gulf War veterans. Further investigation is ongoing.
Source: GARD

Question: How to diagnose Amyotrophic lateral sclerosis ?
Answer: Is genetic testing available for amyotrophic lateral sclerosis? Yes. Clinical genetic testing is currently available for several genes in which mutations are known to cause ALS. Genetic testing on a research basis is also available for select susceptibility genes associated with ALS. You can find laboratories offering clinical and research genetic testing for ALS on a Web site called GeneTests. To see GeneTests' list of the types of ALS for which genetic testing is available, click here. Click on "Testing" next to each type of ALS of interest to see a list of the laboratories that offer clinical testing. Click on "Research" next to each type of ALS of interest to see a list of the laboratories that offer research testing. Please note that most of the laboratories listed through GeneTests do not accept direct contact from patients and their families. Therefore, if you are interested in learning more, you will need to work with a health care provider or a genetics professional.
Source: GARD