None of the patients in the present study had mutations in C9ORF72. Hexanucleotide (GGGGCC) repeat expansion in a non-coding region of C9ORF72 is the major genetic cause of FTD and ALS (c9FTD/ALS) in the Caucasian population [49], but extremely rare in Japan [38, 50, 51]. Here, C9orf72 is linked to frontotemporal dementia.