Mutations within microtubule-associated protein tau (MAPT) (Hutton et al., 1998), granulin (GRN) (Baker et al., 2006; Cruts et al., 2006), and chromosome 9 open reading frame 72 (C9orf72) (DeJesus-Hernandez et al., 2011; Renton et al., 2011) are proven major causes of genetic FTD, accounting for 10–20% of all FTD cases. This evidence concerns the gene C9orf72 and frontotemporal dementia.