Gao D et al. study revealed the level of cystatin C in active stage of systemic lupus erythematosus was higher than that in stable stage (P < 0.05), the increase degrees are negatively correlated with the inner diameter of brachial artery, which implied a correlation of serum cystatin C and vascular endothelial cell injury [25]. The gene discussed is CST3; the disease is systemic lupus erythematosus.