Mutations in GLRX5, which connects the first step of the ISC machinery to its last step, as well as mutations in the accessory proteins, which are involved in the late-acting step of the ISC machinery devoted to mitochondrial [4Fe-4S]-binding protein biogenesis, cause different Fe-S cluster-related diseases, such as sideroblastic anemia, muscle myopathy, multiple mitochondrial disfunction syndromes 1 to 5, and complex I deficiency [23,30,47,48,49]. Here, GLRX5 is linked to sideroblastic anemia.