Hemoglobin S–β-thalassemia disease is a hemoglobinopathy (see Sidebar 1: Anemias Caused by Hemolysis: Hemoglobinopathies) that causes symptoms similar to those of sickle cell disease, but milder.

Because of the increased frequency of both Hb S and β-thalassemia genes in similar population groups, inheritance of both defects is relatively common. Clinically, the disorder causes symptoms of moderate anemia and signs of sickle cell anemia, 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 Hb 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 for sickle cell disease.

Last full review/revision February 2009 by Alan E. Lichtin, MD