This percentage encompasses the EOFAD variants, caused by inherited fully penetrant autosomal dominant mutations in the amyloid protein precursor (APP), or PSEN1, PSEN2 that constitute the γ-secretase apparatus [87], and changes in their function increases the production of Aβ42 oligomers and/or deposition of amyloid plaques. Here, PSEN2 is linked to early-onset autosomal dominant Alzheimer disease.