[Impact of C9orf72 on Japanese Patients with Amytrophic Lateral Sclerosis (ALS)/Frontotemporal Dementia (FTD)].

In 2011, C9orf72 hexanucleotide (GGGGCC) repeat expansion (HRE) in intron 1 was reported as the most common cause of sporadic and familial amyotrophic lateral sclerosis (ALS)/frontotemporal dementia (FTD) in the Caucasian population. In the Japanese population, the C9orf72 repeat expansion was found to account for 0.2% cases of sporadic ALS and 2.6% of familial ALS. Notably, among individuals in the Kii peninsula which has recorded high incidence of ALS or ALS/PDC (parkinsonism-dementia complex), the frequency of C9orf72 repeat expansion was 20% (3/15) indicating high prevalence. It is important to obtain detailed family history of ALS and FTD to understand the cause of the diseases including the C9orf72 mutation.