Alpha thalassemia and the hematology of homozygous sickle cell disease in childhood

ABSTRACT

Alpha thalassemia modifies the gematolic expression of homozygous sickle cell (SS) disease, resulting in increased total hemoglobin and HbA2 and decreased HbF, mean cell volume, reticulocytes, irreversibly sickled cells, and biliru-bin levels. The age at which these changes develop in children with SS disease is unknown. Ascertainment of globin gene status in a large representative sample of study the gematologic indices in nine children homozygous for Alpha thalassemia 2 (two-gene group), 90 children heterozygous for Alpha thalassemia 2 (three-gene group), and 167 children with a normal Alpha globin gene complement (four-gene group). The two-gene group had significantly lower mean cell volumes from birth, higher red cell counts from one month, lower reticulocytes from three months, and higher HbA2 levels from one year, as compared with the four-gene group. Children with three genes had intermediate indices but resembled more closely the four-gene group. Differences in total hemoglobin or in fetal hemoglobin between the groups were not apparent by eight years of age. The most characteristic differences of the two-gene group were the raised proportional HbA2 level and low mean cell volume, the latter having some predictive value for Alpha thalassemia status at birth.(AU)