This CKD–oxidative stress association has been shown in all CKD stages after observing (i) increases in oxidative stress biomarkers such as oxidized low-density lipoprotein, oxidized thiol compounds, and malondialdehyde; (ii) increase in biomarkers related to DNA damage by ROS such as 8-hydroxydeoxyguanosine and 8-oxodeoxyguanosine; and (iii) deterioration in antioxidant defense due to the inability to eliminate ROS, through alteration in the activity of the enzymes superoxide dismutase, myeloperoxidase, xanthine oxidase, heme-oxidase, glutathione peroxidase, or catalase [9,10]. The gene discussed is XDH; the disease is chronic kidney disease.