In view of the abnormal Tau “processing” that we initially detected in HD brains (Fernández-Nogales et al., 2014) that leads to an alteration of 4R-Tau/3R-Tau ratio in favor of 4R-Tau isoforms (similar to that seen in some FTD forms caused by intronic Tau mutations), we explored the possibility of Tau deposits in HD brains. This evidence concerns the gene MAPT and frontotemporal dementia.