HAMP and hemochromatosis: Subsequent work demonstrated that the relatively more predominant 1q-linked form of juvenile hemochromatosis (subtype 2A; OMIM #602390) is caused by inactivation of the HJV gene encoding hemojuvelin that severely suppresses hepcidin expression (71), while the 1q-unlinked form (subtype 2B; OMIM #613313) is directly caused by inactivation of the HAMP gene encoding hepcidin (72).