APOE and early-onset autosomal dominant Alzheimer disease: Apolipoprotein E (APOE) is a protein that plays an important role in lipid metabolism (including cholesterols) and has been implicated in synaptogenesis, repair of injured nerve tissue and the modulation of beta-amyloid plaques and neurofibrillary tangles that characterise Alzheimer’s disease (AD) (for review, see Belloy et al., 2019; Rocchi et al., 2003).