Recently, Zhao et al. (2018) found that knockdown of Bdh2 expression caused increased DNA hydroxymethylation and decreased DNA methylation in CD4+ T cells, proposing the association between Bdh2 and DNA demethylation in the pathogenesis of systemic lupus erythematosus, and they revealed that the Bdh2 knockdown induced DNA hypomethylation was associated with increasing intracellular iron in CD4+ T cells. Here, BDH2 is linked to systemic lupus erythematosus.