C9orf72 and dementia: Although sporadic forms of FTLD are still poorly understood due to the absence of a clear genetic etiology, 30–50% of patients with FTLD present a positive family history of dementia, with most of them carriers of mutations in genes known to be pathogenic for the disease [6,7,8], such as the chromosome 9 open reading frame (C9orf72) [9,10], the granulin precursor (GRN) [11,12], and the MAPT genes [13,14].