PSEN2 and Alzheimer disease: Fewer than 1% of AD cases are known to be familial, caused by inheritance of rare autosomal dominant mutations [5] of amyloid precursor protein (APP) gene, presenilin 1 (PSEN1), and presenilin 2 (PSEN2), where PSEN1 and PSEN2 are involved in the processing of APP to amyloid-beta (Aβ) [6].