What is the difference between sporadic and familial ALS?

The main difference between sporadic and familial cases of amyotrophic lateral sclerosis (ALS) is whether or not there is a family history of the disease. When ALS affects more than one person in the same biological family, it’s referred to as familial ALS. The term sporadic ALS, on the other hand, is used to refer to any case of ALS in which there is no known family history of the disease. Sporadic ALS accounts for the vast majority — about 90% — of ALS cases.