Although AI, mainly mediated by the IL-6–hepcidin axis, is considered the most frequent cause of anemia in RA, iron deficiency anemia (IDA), sometimes caused by gastrointestinal blood loss associated with the use of non-steroidal anti-inflammatory drugs, has been estimated to be the second most common form of anemia in RA. The gene discussed is HAMP; the disease is Iron deficiency anemia.