TMEM106B and frontotemporal dementia: We present a GRN family with a proband presenting with classical young-onset FTD whose parent is an asymptomatic carrier in their 80s, possibly protected from developing disease symptoms because of the modifying effect of TMEM106B. This report is in line with our previously reported TMEM106B genetic study in unrelated GRN patients, in which very few of the symptomatic GRN carriers were homozygous for the TMEM106B protective haplotype (4), and suggests that the presence of at least one TMEM106B risk haplotype is required - as a permissive haplotype - to develop FTLD-GRN.