C9orf72 and frontotemporal dementia: A large hexanucleotide (GGGGCC) repeat expansion (HRE) in the chromosome 9 open reading frame 72 (C9orf72) gene has been identified as the most frequent genetic cause in familial and sporadic patients with ALS and frontotemporal dementia (FTD) in Caucasian populations (3, 4), strongly arguing for a central role of C9orf72 in ALS pathogenesis.