An increase in the number of d(G4C2)•(G2C4) nucleotide repeats (repeat expansion) in the non-coding region of C9orf72 gene has been identified as the most common genetic cause of two devastating neurological disorders, amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) (1,2). Here, C9orf72 is linked to frontotemporal dementia.