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Hemoglobin S–Beta-Thalassemia Disease

By Evan M. Braunstein, MD, PhD, Assistant Professor of Medicine, Division of Hematology, Department of Medicine, Johns Hopkins School of Medicine

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Hemoglobin S–beta-thalassemia disease is a hemoglobinopathy that causes symptoms similar to those of sickle cell disease, but milder.

Because of the increased frequency of both Hb S (the abnormal hemoglobin that is responsible for sickle cell disease) and beta-thalassemia genes in similar population groups, inheritance of both defects is relatively common. Beta-thalassemia results from decreased production of the beta-polypeptide chains of hemoglobin due to either mutations or deletions in the beta globin gene, leading to impaired production of Hb A (see also Thalassemias).

Clinically, Hb S–beta-thalassemia causes symptoms of moderate anemia and signs of sickle cell disease, which are usually less frequent and less severe than those of sickle cell disease. Mild to moderate microcytic anemia is usually present along with some sickled RBCs on stained blood smears.

Diagnosis requires quantitative hemoglobin studies. The Hb A2 is > 3%. Hb S predominates on electrophoresis, and Hb A is decreased or absent. Hb F increase is variable.

Treatment, if necessary, is the same as treatment of sickle cell disease.