C9orf72 and frontotemporal dementia: Since identification of mutations in the gene of microtubule-associated protein tau(MAPT) as a cause of monogenic FTD in 1998,7 mutations in overten other genes have been identified, such as in the progranulin gene(GRN) in 2006, and in C9orf72 (Chromosome 9open reading frame 72) in 2011.8-11 Mutations in MAPT,GRN and C9orf72 are the most commonly reportedin FTD cohorts worldwide.