Less than 5% of AD patients manifest symptoms at an earlier stage (before the age of 65), i.e., familial AD (FAD), which is linked to genetic mutations in one of three genes, including, amyloid precursor protein (APP), presenilin1 (PSEN1) and presenilin 2 (PSEN2) [11]. This evidence concerns the gene PSEN1 and familial Alzheimer disease.