C9orf72 and frontotemporal dementia: While the frequency of C9orf72 repeat expansions (6.6%) and of GRN variants (5.8%) is in concordance with the reported European frequencies,28, 29 indicating that our subject cohort was broadly comparable to other FTD screening cohorts, we did not detect any probable pathogenic variants in MAPT and TBK1. Pan-European frequencies are reported at about 8% for MAPT29 and 0.4% for TBK1,30 with frequencies up to 17.8% for MAPT31 and 1.7% for TBK132 in Dutch and Belgian populations, respectively.