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For further information, see CMDT Part 13-05: Sideroblastic Anemia

Key Features

  • Heterogeneous group of disorders in which reduced hemoglobin synthesis occurs because of reduced ability to synthesize heme or an impaired ability to incorporate heme into protoporphyrin IX

  • Iron accumulates, particularly in mitochondria

  • Modern classification divides sideroblastic anemia into two categories

    • Dyserythropoiesis (ie, hypohepcidinemia)

    • Transfusion-dependence (eg, myelodysplastic syndrome, thalassemia)

  • Most often it is a subtype of myelodysplastic syndrome

  • Other causes include chronic alcohol use disorder (alcoholism), lead poisoning, copper deficiency (hypocupremia), medications (isoniazid, chloramphenicol), and chronic infection or inflammation

  • Inherited forms are usually X-linked but rare recessive forms have been documented

Clinical Findings

  • Symptoms of anemia; no other specific clinical features

  • Hypocupremia

    • Normocytic anemia in two-thirds of cases; macrocytic in remainder

    • Zinc level is usually elevated

    • Neutropenia or thrombocytopenia may be present

    • Myelopathy or demyelinating peripheral neuropathy in some patients


  • Anemia usually moderate, hematocrit 20–30%

  • Mean corpuscular volume

    • Usually normal or slightly increased in sideroblastic subtype of myelodysplastic syndrome

    • Usually low in other subtypes (especially inherited forms), leading to confusion with iron deficiency

  • Peripheral blood smear characteristically shows dimorphic population of RBCs: 1 normal and 1 hypochromic

  • Coarse basophilic stippling of RBCs and serum lead level elevated in lead poisoning

  • Bone marrow iron stain shows generalized increase in iron stores and ringed sideroblasts (RBCs with iron deposits encircling the nucleus) and marked erythroid hyperplasia (resulting from ineffective erythropoiesis)

  • Serum iron level and transferrin saturation are high


  • Occasionally, transfusion is required for severe anemia

  • Recombinant erythropoietin therapy is not usually effective

  • Oral pyridoxine (50–200 mg/day) occasionally useful

  • Removal of offending toxins and drugs is needed in the secondary acquired forms

  • Hypocupremia: administer copper sulfate (2.5 mg orally twice daily)

    • Associated with high hematologic response rate but low neurologic response rate

    • Exogenous or endogenous zinc exposure needs to be eliminated

  • Luspatercept

    • FDA approved for myelodysplastic syndrome with ringed sideroblasts

    • It is a TGF-β ligand trap that promotes erythroid maturation and reduces need for transfusion

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