Familial AD results from a genetic mutation in the APP gene or in the presenilin 1 and 2 (PS1 and PS2) genes that lead to an altered ratio of amyloid β42 to amyloid β40 and eventually rapid aggregation of Aβ peptide to form Aβ plaque (Bettens et al., 2013). This evidence concerns the gene APP and Alzheimer disease.