C9orf72 and frontotemporal dementia: Of the 38 individuals who developed subsequent features, regardless of C9orf72 status, 27 did so prior to the discovery of C9orf72 expansions in FTD and ALS in 2011.3,4 Of the 26 individuals with a C9orf72 expansion who developed subsequent features, 16 did so prior to 2011.