CYP46A1 and Alzheimer disease: Interestingly, patients with AD and the CYP46A1 TT genotype seem to have the highest level of plasma 24-OHC (Li et al., 2018), which suggests that the CYP46A1 rs754203 polymorphism may play a role in mediating the increased risk of AD by causing differences in blood 24-OHC concentration levels.