C9orf72 and frontotemporal dementia: Data on genetic variants were available for APOE ε4 (positive n = 26, negative n = 74, Table 1), C9orf72 variations (positive n = 8 [all FLTD-TDP], negative n = 92), GRN variations (positive n = 5 [1 AD, 4 FTLD-TDP], negative n = 95), and MAPT variations (positive n = 2 [both classified as other, with FTD-PPA syndromes], negative n = 96).