APOE and early-onset autosomal dominant Alzheimer disease: The apolipoprotein E (APOE) ε4 allele, a well-known risk locus for Alzheimer’s disease, has also been identified as a strong genetic risk factor for developing Parkinson’s disease dementia/dementia with Lewy bodies.11  APOE4 promotes amyloid-beta oligomerization and its pathological accumulation.23 The role of APOE4 in dementia with Lewy bodies pathogenesis is still unclear.