Whilst to date no causative genes have been conclusively connected with the sporadic or late onset form of the disease (LOAD), several mutations have been identified in specific genes associated with the development of familial or inherited AD: amyloid precursor protein, presenilin-1, presenilin-2, and apolipoprotein E. Familial AD frequently manifests at earlier ages and is therefore referred to as early onset AD (EOAD); its clinical manifestations and progression are typically more aggressive than those of sporadic AD [3,4]. The gene discussed is PSEN1; the disease is Alzheimer disease.