C9orf72 and sporadic amyotrophic lateral sclerosis: While the overall percentage of pathogenic variants in fALS is very high ranging from 50 to 85%,4,5 the reported proportion of pathogenic variants in sporadic amyotrophic lateral sclerosis (sALS) is highly variable depending on the respective study and population, ranging from 7.4% for European sALS to 2.9% for Japanese sALS.6 Furthermore, many studies focused on key genes only, such as C9orf72, SOD1, TARDBP and FUS, making an overall estimation of ALS-associated variants in sALS difficult.