APOE and early-onset autosomal dominant Alzheimer disease: Previous studies conducted in predominantly European-ancestry populations have demonstrated that apolipoprotein E (APOE [OMIM 107741]) ε2 and ε4 alleles potently increase risk of lobar ICH.10 In Alzheimer disease, another disorder associated with APOE ε allele status, the degree of risk contributed by APOE genotype varies substantially by the ancestry of the population studied.