MSTN and rheumatoid arthritis: Although there was no significant difference in medications between RA patients with serum myostatin subgroups or four subgroups by myostatin and myopenia categorization during one-year follow-up, and serum myostatin was still the risk factor of one-year radiographic progression after adjustment for potential confounders, it would be necessary to recruit more treatment-naïve patients and use the same treatment regimen to remove this confounding effect.