These clinical conditions share overlapping common genetic risk factors, including variation in the SNCA and GBA genes, but also have distinct genetic components such as the apolipoprotein E ε4 (APOE4) genotype, which is a strong risk factor for DLB but not PD, and the MAPT H1 haplotype, a strong risk factor for PD but not DLB.3, 4, 5. This evidence concerns the gene APOE and Parkinson disease.