High levels of neurofilament light chain (NfL) in CSF and blood show high sensitivity for identifying patients with neurodegenerative diseases compared to healthy controls, but this is neither specific to bvFTD nor to tau or TDP-43 in general (Vijverberg et al., 2017; Karantali et al., 2020). This evidence concerns the gene MAPT and behavioral variant of frontotemporal dementia.