Compared with low myostatin group, RA patients with high myostatin had significantly lower level of ΔASMI (-0.03 ± 0.41 kg/m2vs. 0.09 ± 0.39 kg/m2, P=0.003), indicating that high serum myostatin at baseline may contribute to reduction of skeletal muscle mass after one-year follow-up. This evidence concerns the gene MSTN and rheumatoid arthritis.