PSEN2 and Alzheimer disease: Studies on familial forms of early-onset AD (EOAD) happening before 65 years of age have highlighted the crucial role of precise mutations in the amyloid precursor protein (APP), presenilin 1 (PSEN1), and presenilin 2 (PSEN2) genes; however, these rare familial forms of AD account for less than 1% of the cases [5].