At the neuropathological level, DS and AD share several features that are characterized by the presence of amyloid plaques and neurofibrillary tangles (NFTs), the formation of which is affected by the aberrant phosphorylation of Tau (for NFTs), as well as of amyloid precursor protein (APP) and presenilin 1 (PS1) (for amyloid plaques) (Johnson and Hartigan, 1999; Tiraboschi et al., 2004). Here, PSEN1 is linked to Alzheimer disease.