C9 and frontotemporal dementia: In 2011, a common basis for ALS and FTD was identified as a hexanucleotide repeat expansion of the G4C2 (HRE) in the non-coding region of the chromosome 9 open reading frame 72 (C9orf72) gene, referred as C9-FTD/ALS (DeJesus-Hernandez et al., 2011; Renton et al., 2011).