The principal hallmark of Alzheimer’s disease is the appearancein the hippocampal region of the brain4 of proteinaceous deposits inside neuronal cells, called neurofibrillarytangles, mainly constituted by fibrillar aggregates of phosphorylatedtau protein,5 and in the extracellularspace, called amyloid plaques, mainly constituted by fibrillar aggregatesof amyloid beta protein (Aβ).6 Amyloidβ protein is the final product of the aberrant cleavage of amyloidprecursor protein (APP).7 The gene discussed is APP; the disease is early-onset autosomal dominant Alzheimer disease.