TARDBP and behavioral variant of frontotemporal dementia: Though further multicenter studies are required to confirm the association between serum HERV-K levels and to clarify the link between HERV-K and TDP-43 pathology, our study has provided new insights into an unrecognized perturbed pathology in bvFTD and opened a new area of research for understanding the pathogenesis of bvFTD with TDP-43 pathology.