We analyzed 1,396 FTLD cases gathered through the International FTD Genetics Consortium (IFGC) (ifgcsite.wordpress.com/) phase III initiative, aiming at (1) characterizing C9orf72 expansions in relation to genetic ancestry and AAO and (2) assessing the usefulness of these measures in discriminating the behavioral from the language variant syndrome. Here, C9orf72 is linked to frontotemporal dementia.