Mutations in the amyloid precursor protein (APP) and the presenilin genes (PS1 and PS2), which are both linked to the familiar form of AD (e.g., Goate et al., 1991), have been described to lead to a massive increase in cytotoxic Aβ40 and Aβ42 oligomers (e.g., Walker et al., 2005; Theuns et al., 2006). This evidence concerns the gene APP and Alzheimer disease.