Early/familial-onset AD (EOAD/FAD) is associated with autosomal dominant mutations in genes encoding for APP as well as PSEN1/2 (presenilin 1 and 2), the catalytic subunit of γ-secretase, resulting in the overproduction of the insoluble toxic Aβ [18,19]. The gene discussed is PSEN1; the disease is familial Alzheimer disease.