In particular, the identification of an increased hexanucleotide repeat expansion (GGGGCC) in the c9orf72 gene on chromosome 9p21.1 [70,71] which accounts for over 40% of familial and approximately 8% of apparently “sporadic” ALS cases [70,71,72] has radically altered the understanding of ALS pathogenesis. The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.