Sickle cell syndromes. I. Hemoglobin SC α thalassemia

Abstract

A 7 year old black child with hemoglobin SC disease and microcytosis was found by hematologic and globin synthesis studies to have concomitant α thalassemia. Genetic studies of the family supported this diagnosis and, in addition, disclosed the presence of hemoglobin H disease in an infant sibling. The child with HbSC α thalassemia demonstrated more severe anemia and a more hemolytic picture than is typical of HbSC disease. Her erythrocytes exhibited decreased osmotic fragility in comparison to HbSC erythrocytes, but an indistinguishable oxygen equilibrium curve and level of 2,3 DPG. Erythrocyte sickling, however, was significantly reduced, with less than 35% sickle forms present at nearly complete oxygen desaturation. The sibling with hemoglobin H disease exhibited 26% Bart's (γ4) hemoglobin at birth, a level comparable with that seen in infants with HbH disease in Far Eastern populations. At age 5 months typical findings of mild HbH disease appeared, with HbH making up 6.5% of the total hemoglobin.