Since hepcidin impairs intestinal iron absorption and recycling by inhibiting ferroportin-mediated iron export from enterocytes and macrophages, patients with TMPRSS6-related iron refractory iron deficiency anemia (IRIDA) develop microcytic anemia with remarkably low transferrin saturation (TSAT), low–normal ferritin levels, and a poor response to oral iron treatment [5,7,8,9,10,11,12]. The gene discussed is HAMP; the disease is microcytic anemia.