high. The RDW is increased with the red blood cell histogram shifted to the left. Leukocytes and platelets are normal. Bone marrow shows erythroid hyperplasia with a maturation arrest.In excess of 40% of the developing erythrocytes are ringed sideroblasts. Serum iron, percentage saturation and ferritin are increased. The total iron-binding capacity of the cells is normal to decreased. Stainable marrow hemosiderin is increased. Classification Sideroblastic anemia is typically divided into subtypes based on its cause. Hereditary or congenital sideroblastic anemia may be X-linked or autosomal. GLRX5 has also been implicated. Acquired, or secondary, sideroblastic anemia develops after birth and is divided according to its cause. Laboratory findings Serum Iron: high increased ferritin levels decreased total iron-binding capacity high transferrin saturation Hematocrit of about 20-30% The mean corpuscular volume or MCV is usually normal or low for congenital causes of sideroblastic anemia but normal or high for acquired forms. With lead poisoning, see coarse basophilic stippling of red blood cells on peripheral blood smear Specific test: Prussian blue stain of RBC in marrow shows ringed sideroblasts. Prussian blue staining involves a non-enzymatic reaction of ferrous iron with ferrocyanide forming ferric-ferrocyanide, which is blue in color. A counterstain may be used to provide better visualization. Treatment Occasionally, the anemia is so severe that support with transfusion is required. These patients usually do not respond to erythropoietin therapy. Some cases have been reported that the anemia is reversed or heme level is improved through use of moderate to high doses of pyridoxine (vitamin B6). In severe cases of SBA, bone marrow transplant is also an option with limited information about the success rate. Some cases are listed on MedLine and various other medical sites. In the case of isoniazid-induced sideroblastic anemia, the addition of B6 is sufficient to correct the anemia. Deferoxamine, a chelating agent, is used to treat iron overload from transfusions. Therapeutic phlebotomy can be used to manage iron overload. Prognosis Sideroblastic anemias are often described as responsive or non-responsive in terms of increased hemoglobin levels to pharmacological doses of vitamin B6. 1- Congenital: 80% are responsive, though the anemia does not completely resolve. 2- Acquired clonal: 40% are responsive, but the response may be minimal. 3- Acquired reversible: 60% are responsive, but course depends on treatment of the underlying cause. Severe refractory sideroblastic anemias requiring regular transfusions and/or that undergo leukemic transformation (5–10%) significantly reduce life expectancy. See also Anemia