BMP6 and IRIDA syndrome: MT-2 (matriptase-2, TMPRSS6, transmembrane protease serine 6) is ubiquitously expressed in the liver, invalid of MT-2 due to genetic mutation causes iron-refractory iron deficiency anemia (IRIDA) [51, 52], and MT-2 is also downregulated by iron and BMP6 [53, 54].