Thalassemia and the Hematology of Homozygous Sickle Cell Disease in Childhood

a Thalassemia modifies the hematologic expression of homozygous sickle cell (55) disease, resulting in increased total hemoglobin and HbA2 and decreased HbF. mean cell volume, reticulocytes. irreversibly sickled cells. and bilirubin levels. The age at which these changes develop in children with 55 disease is unknown. Ascertainment of globin gene status in a large representative sample of children with 55 disease has afforded an opportunity to study the hematologic indices in nine children homozygous for a thalassemia 2 (two-gene group). 90 children heterozygous for a thalassemia 2 (three-gene group). and 167 children with a normal a globin gene complement (fourgene group). The two-gene group had significantly lower a Thalassemia 2 is common in black populations, heterozygotes and homozygotes occurring in -30% and 4%, respectively, ofiamaican infants’ and black Americans.2 Inheritance of a thalassemia in homozygous sickle cell (55) disease ameliorates the hematologic features, 7 although observations of clinical benefit are less consistent.4’6 Among older children and adults, homozygous a thalassemia 2 resulted in higher levels of total hemoglobin, hematocrit, red cell count, and HbA2, and lower levels of HbF, mean cell volume, reticulocytes, and irreversibly sickled cells. These findings were compatible with reduced hemolysis, which was supported by a prolonged red cell survival.8 Whether these changes occur in young children is unknown, as is the age at which the changes develop. In the Jamaican sickle cell cohort study, the effects of a thalassemia on the development of hematologic changes in 55 disease from birth have been observed.