Apart from genes encoding amyloid precursor protein (APP), presenilin-1 (PSEN1) and presenilin-2 (PSEN2) that are linked to rare familial cases of disease, polymorphisms in apolipoprotein E gene (APOE) are considered as the most prevalent AD risk factors in the sporadic type of disease [39,40]. The gene discussed is APOE; the disease is Alzheimer disease.