C9orf72 and frontotemporal dementia: Baseline NfL was significantly higher in FTD participants with a GRN mutation compared to participants with no mutation (p = 1.6E-12), and higher in GRN mutation carriers when compared to C9orf72 (p = 2.7E-06) or MAPT (p = 9.5E-08) mutation carriers (Fig. 6b, Tables S27 and S28).