A minority of Alzheimer’s disease cases are associated with genetic mutations in the genes encoding APP (amyloid precursor protein), PSEN1 (presenilin 1), and PSEN2 (presenilin 2), and they are typically linked to early-onset Alzheimer’s disease (EOAD), in which symptoms generally appear before the age of 65. This evidence concerns the gene PSEN2 and early-onset autosomal dominant Alzheimer disease.