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Sideroblastic anemias are iron-utilization anemias that are generally part of a myelodysplastic syndrome, producing a normocytic-normochromic anemia with high RBC distribution width or a microcytic-hypochromic anemia, particularly with increased serum iron, ferritin, and transferrin saturation.

Sideroblastic anemias are among the anemias characterized by inadequate marrow utilization of iron for Hb synthesis despite the presence of adequate or increased amounts of iron (iron-utilization anemias). Other iron-utilization anemias include some hemoglobinopathies, primarily thalassemias (see Anemias Caused by Hemolysis: Thalassemias). Sideroblastic anemias are characterized by the presence of polychromatophilic, stippled, targeted RBCs (siderocytes). Sideroblastic anemias are generally part of a myelodysplastic syndrome but may be hereditary or may occur secondary to drugs (eg, chloramphenicol Some Trade Names
CHLOROMYCETIN
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, cycloserine Some Trade Names
SEROMYCIN
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, isoniazid Some Trade Names
INH
NYDRAZID
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, pyrazinamide Some Trade Names
No US trade name
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) or toxins (including ethanol and lead). Deficient reticulocyte production, intramedullary death of RBCs, and bone marrow erythroid hyperplasia (and dysplasia) occur. Although hypochromic RBCs are produced, other RBCs may be large, producing normochromic indices; if so, variation in RBC size (dimorphism) usually produces a high RBC distribution width (RDW).

Sideroblastic anemia is suspected in patients with microcytic anemia or a high RDW anemia, particularly with increased serum iron, serum ferritin, and transferrin saturation (see Anemias Caused by Deficient Erythropoiesis: Iron Deficiency Anemia). The peripheral smear shows RBC dimorphism. RBCs may appear stippled. Bone marrow examination is necessary and reveals erythroid hyperplasia; iron staining reveals the pathognomonic iron-engorged paranuclear mitochondria in developing RBCs (ringed sideroblasts). Other features of myelodysplasia are frequently evident. Serum lead is measured if sideroblastic anemia has an unknown cause.

Ring Sideroblasts in Sideroblastic Anemia

Elimination of a toxin or drug (especially alcohol) can lead to recovery. Rarely, congenital cases respond to pyridoxine 50 mg po tid, but incompletely.

Last full review/revision November 2005

Content last modified November 2005