APOE and early-onset autosomal dominant Alzheimer disease: Notably, the APOE4-allele is the most important genetic risk factor for Alzheimer’s disease and a risk factor of atherosclerosis, while APOE2 is protective for Alzheimer disease and atherosclerosis (except if associated with type III familial hyperlipiproteinemia) (Mahley et al. 2009; Herz and Beffert 2000; Davignon et al. 1988).