The majority of cases are termed sporadic, caused by a combination of genetic and environmental factors, while less than 2% of cases are termed familial Alzheimer’s disease (FAD) [1], caused by mutations in one of three genes: PSEN1, PSEN2, or APP, which each play a role in the generation of amyloid-β peptides [2]. The gene discussed is PSEN1; the disease is familial Alzheimer disease.