APOE and early-onset autosomal dominant Alzheimer disease: Since its discovery in the early 90’s, APOE polymorphism has remained the strongest identified genetic factor affecting risk of late-onset Alzheimer’s disease (LOAD) with the ε4 allele being associated with increased disease occurrence [25, 26, 119], while the ε2 allele effectively lowering the risk among ε4 allele non-carriers [24, 88].