APP and familial Alzheimer disease: Most AD cases belong to the sporadic form of AD, with a disease onset after the age of 65 (late-onset Alzheimer’s disease (LOAD)), and only approximately 5% of AD cases are caused by mutations in the genes encoding for APP or PS1/PS2 (familial Alzheimer’s disease FAD), leading to an increased production of highly amyloidogenic Aβ42 peptides.