There have been identified four major genes associated with inherited risk for AD: presenilin-1, presenilin-2, amyloid precursor protein (APP), and apolipoprotein E. Mutations in these genes cause dysregulation of amyloid precursor protein processing, and in particular of the handling of a proteolytic derivative termed beta-amyloid (Abeta) that ultimately causes neuronal dysfunction and death [2]. Here, PSEN1 is linked to Alzheimer disease.