All these conditions are known to be pathologically linked, often arising from either tau or TDP-43 accumulation; for instance, TDP-43 is the usual cause of svPPA and approximately half of bvFTD cases, while the other half of bvFTD patients and many nfvPPA cases are associated with tau pathology (Perry and Miller, 2013). This evidence concerns the gene TARDBP and behavioral variant of frontotemporal dementia.