Sporadic ALS is the most common form of the disease, accounting for around 90% to 95% of all cases. It is diagnosed in patients who do not have a family history of ALS. Genetic factors can slightly increase the risk of developing sporadic ALS, but they do not directly cause the disease itself. Familial, or inherited, ALS runs in families and accounts for the remaining 5% to 10% of cases. It can be caused by one of several mutations that are passed from parents to their children.