C9orf72 and frontotemporal dementia: A hexanucleotide repeat expansion (HRE) located in the 5′ UTR region of C9ORF72 gene is the most common genetic cause of familial frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) (DeJesus-Hernandez et al., 2011; Renton et al., 2011; Gijselinck et al., 2012).