A previous study, comparing DNA methylation between AMD patients and age-matched controls, revealed that glutathione S-transferase isoforms mu1 (GSTM1) and mu5 (GSTM5) undergo epigenetic repression in AMD RPE/choroid via promoter hypermethylation, which, in turn, decreased mRNA and protein levels [45]. This evidence concerns the gene GSTM1 and age-related macular degeneration.