In 2011, a (G4C2)n repeat expansion upstream of the coding region of C9orf72 was found to cause frontotemporal lobar degeneration (FTLD) and/or amyotrophic lateral sclerosis (ALS) in about 10% of all Caucasian patients with these related fatal neurodegenerative conditions (DeJesus‐Hernandez et al, 2011; Renton et al, 2011; Gijselinck et al, 2012). This evidence concerns the gene C9orf72 and frontotemporal dementia.