As a result, postmortem examinations of brain tissue from patients with Alzheimer’s disease have revealed that APOE4 exacerbates the accumulation of intra-neuronal Aβ, initiates the formation of Aβ oligomers, and diminishes Aβ clearance through microglial phagocytosis as well as the drainage of interstitial fluid (ISF) [9,223,300]. The gene discussed is APOE; the disease is early-onset autosomal dominant Alzheimer disease.