Only familial AD (5% of cases) is due to the overproduction of Aβ because of mutations in the amyloid precursor protein (APP) gene or in the APP processing enzymes [7, 8], while the greater part (95%) of the so-called sporadic AD cases are probably caused by dysfunctions in Aβ aggregation, degradation, and removal [5, 9]. Here, APP is linked to Alzheimer disease.