Moreover, female predominance during the reproductive phase is a key characteristic of SLE; evidence suggests this may be partially due to increased estrogen levels during the reproductive phase [47,48], as Liu and colleagues [49] demonstrated reduced DNA methylation within the estrogen receptor 1 (ESR1) gene in women with SLE and RA patients in comparison to healthy controls. This evidence concerns the gene ESR1 and systemic lupus erythematosus.