Approximately 5-10% of cases of ALS are familial ALS. More than 25 different genes could be linked to the causation of familial ALS. However, the remaining majority 90-95% of ALS cases are Sporadic ALS. There is no known cause for  Sporadic ALS.
Amyotrophic lateral sclerosis causes
Bell's palsy pathophysiology
Amyotrophic lateral sclerosis classification
Parkinson's disease causes
Amyotrophic lateral sclerosis risk factors
Fragile X syndrome causes
Parkinson's disease other imaging findings
Acute disseminated encephalomyelitis causes