Our results demonstrate that vitamin D supplementation significantly ameliorates oxidative stress in MS: reducing serum MDA (a marker of lipid peroxidation) and TOS (total oxidant status), while increasing TAC (total antioxidant capacity) and the activity of key antioxidant enzymes SOD (superoxide dismutase), CAT (catalase), and GPx (glutathione peroxidase). The gene discussed is CAT; the disease is myeloid sarcoma.