What is the difference between familial and genetic ALS?

The difference between familial and genetic ALS lies in the family history of the disease. Familial ALS (FALS) is present when several members of a family are affected by ALS (or have had the disease in the past). In contrast, the term “genetic ALS” is used when a genetic mutation is detected in one of the known ALS genes—regardless of whether other family members have the disease or not. This means that even without a family history of ALS, genetic ALS can be diagnosed if a corresponding mutation is present. The terms “familial ALS” and “genetic ALS” overlap—but they are not synonymous.