An intronic hexanucleotide repeat expansion (GGGGCC)n in the C9orf72 gene is the most frequent genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) (Couthouis et al, 2011; DeJesus‐Hernandez et al, 2011; Renton et al, 2011). This evidence concerns the gene C9orf72 and frontotemporal dementia.