Since the initiation of tocilizumab and TNF-α inhibitor treatments resulted in down-regulation of both serum hepcidin and ferritin levels, and since a strong correlation between serum hepcidin and ferritin was observed throughout the treatment period, it is speculated that improvement in anemia was generated by improved iron utilization through hepcidin downregulation. The gene discussed is HAMP; the disease is anemia (phenotype).