Only approximately <5% of the AD cases are familial forms of autosomal dominant inheritance and are generally characterized by an early-onset and associated to genetic mutations in some proteins (e.g., presenilin 1, presenilin 2, amyloid-β protein precursor AβPP), while 95% cases of AD are late-onset and sporadic, resulting from a complex interaction of genes and environmental factors [19]. The gene discussed is PSEN1; the disease is Alzheimer disease.