fAD has an autosomal dominant inheritance pattern with early onset (< 65 years) and mutations in genes that encode amyloid precursor protein (APP), presenilin 1 (PSEN1) or presenilin 2 (PSEN2), which increase Aβ production and accumulation, considered to be causes of fAD [121–126]. Here, PSEN1 is linked to familial Alzheimer disease.