CAT and systemic lupus erythematosus: Also, increased malondialdehyde (MDA) a lipid peroxidation marker [19–21] and altered antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) in the patients with SLE [19,20,22] has been described, confirming the altered oxidative stress responses in SLE [23].