Converging clinical and pathological evidence has consistently indicated the apolipoprotein E (APOE) ε4 allele is the best established genetic risk factor for the progression of early AD [13-15], accelerating episodic memory decline [16], and conversion of aMCI to AD [17], whereas the protective APOEε2 allele appears to be against the disease [14, 15, 18, 19], and improvement of episodic memory over time [20]. The gene discussed is APOE; the disease is Alzheimer disease.