C9orf72 and frontotemporal dementia: An intronic G4C2 hexanucleotide repeat expansion in the first intron or alternative promoter of the uncharacterized C9ORF72 gene was identified as the cause of amyotrophic lateral sclerosis (ALS), frontotemporal lobar degeneration (FTLD), and ALS-FTLD syndrome linked to chromosome 9p21 (DeJesus-Hernandez et al., 2011; Gijselinck et al., 2012; Renton et al., 2011).