C9orf72 and frontotemporal dementia: The most recent, but more common discovery, is a genetic mutation in the C9orf72 gene involving a hexanucleotide repeat expansion (GGGGCC) in the first non-coding intron of the gene, responsible for both familial and sporadic FTD and ALS, but more frequently for the combined FTD-ALS phenotype [2,3,4,5].