The strikingly low NfL level of this participant compared with GRN pathogenic variant carriers within the same age range (65–77 years), also well below the mean value of phenoconverters,40 supports the hypothesis that carrying 2 copies of the minor allele of TMEM106B might offer protection against developing FTD, or at a minimum a delay in disease onset. The gene discussed is TMEM106B; the disease is frontotemporal dementia.