Recently, the pathogenic polyQ expansions of Htt have been diagnosed in patients with frontotemporal dementia (FTD) or ALS, in which the classical TDP-43 pathology is shown along with the Htt aggregates in the frontal cortex from autopsy [176], revealing an etiological relationship between polyQ expansion and FTD or ALS syndrome. Here, HTT is linked to frontotemporal dementia.