In 2011, two independent studies demonstrated that the most common cause of familial forms of Frontotemporal Dementia (FTD) and/or Amyotrophic Lateral Sclerosis (ALS) is the expansion of hexanucleotide repeats within the C9orf72 gene [38, 39]. The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.