The most prevalent identified cause of ALS found in patients of European descent is a hexanucleotide repeat expansion (HRE) in the C9orf72 gene (OMIM 614260), accounting for 40–60% of fALS cases and 5–10% of apparently sporadic ALS cases [3,4]. The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.