Forms of ALS

ALS is currently described under three different classifications:

• Sporadic is the most common form of ALS in the United States, occurring in 90 to 95 percent of all cases. This type of ALS may affect anyone, anywhere.
• Familial, which occurs more than once in a family lineage (genetic dominant inheritance), accounts for a very small number of cases in the United States — just 5 to 10 percent of all cases. In those families, there is a 50 percent chance each offspring will inherit the gene mutation and may develop the disease.
• Guamanian is a term used to describe an extremely high incidence of ALS, which was observed in Guam and the Trust Territories of the Pacific in the 1950s.