C9orf72 and amyotrophic lateral sclerosis: A heterozygous hexanucleotide (GGGGCC) repeat expansion located between the noncoding exons 1a and 1b of C9ORF72 has been recently identified in patients with FTD and/or ALS (DeJesus‐Hernandez et al., 2011; Renton et al., 2011).