While mutations in APP, PSEN1, and PSEN2 in the Aβ-generation pathway may lead to familial AD showing plaques and tangles [47], mutations in MAPT may lead to tangle formation but not plaques, resulting in frontotemporal dementia (FTD) or conditions similar to CBD, PSP, or PiD [37,48]. Here, PSEN1 is linked to frontotemporal dementia.