The aggregation of amyloid-β (Aβ) in the brain has been correlated with pathogenesis of AD, and, although not proven as the cause of AD, it remains a critical biomarker of the disease.2–4 Aβ occurs most frequently as a small protein of 40 or 42 residues and is derived by proteolytic cleavage of amyloid precursor protein (APP).5–7 While Aβ1–42 is expressed at lower levels than Aβ1–40, it is associated with greater cellular toxicity and is a major component of plaque found in AD patients.8,9 The development of aggressive, early onset forms of AD is associated with alterations to the APP. This evidence concerns the gene APP and Alzheimer disease.