APOE and familial Alzheimer disease: Alzheimer disease (AD) is a complex and common progressive neurodegenerative disease that reflects multifactorial gene mutation (i.e., APP, Presenilin (PSEN) 1 and PSEN 2, ApoE4) as a hallmark of the etiology of familial AD (FAD) and Sporadic AD (SAD) in the elderly population [23–25].