A new form of IRIDA due to combined heterozygous mutations of TMPRSS6 and ACVR1A encoding the BMP receptor ALK2

To the editor: The liver expression of the key iron regulator hepcidin is controlled by the bone morphogenetic protein (BMP)/SMAD pathway. BMP signaling requires the ligand (BMP6 or BMP2),[1][1],[2][2] type I (activin receptor-like kinase 2 [ALK2] and ALK3) and type II receptors (ACVR2 and BMPR2),