APP and Alzheimer disease: Autosomal-dominant Alzheimer disease (ADAD) is a genetic disorder that accountsfor less than 1 % of all AD cases [6].It is genetically heterogeneous and has been associated with mutations in theamyloid precursor protein (APP) gene or in thetwo presenilin genes (presenilin-1 and -2 or PSEN1 and PSEN2) [6].