Mice with mono-allelic expression of wild-type (WT) ferroportin [111] and TMPRSS6 knock-out mice with subsequent reduced ferroportin expression on enterocytic membrane, develop iron deficiency anemia with intra-enterocytic iron retention [126] and patients with TMPRSS6 variants develop Iron Refractory Iron Deficiency Anemia (IRIDA) due to impaired intestinal iron absorption [127,128,129]. The gene discussed is TMPRSS6; the disease is anemia.