Although the considerable overlap in gene expression might be explained by the overlap in clinical symptoms and affected brain regions, the group of FTD patients do not show extensive tau pathology as they were classified as Constantinidis type C1 while the PiD patients all showed extensive tau pathology (Constantinidis type A) suggesting that the observed tau pathology is not necessarily indicative for the molecular pathways affected. This evidence concerns the gene MAPT and frontotemporal dementia.