Alpha-Thalassemia changes erythrocyte heterogeniety in sickle cell disease

ABSTRACT

Homozygous alpha thalassemia has the beneficial effect in sickle cell anaemia of reducing the hemolytic severity while changing several other hematological parameters. We examined in detail some of these hematological alterations. We find that the broad distribution in erythrocyte density and the large proportion of dense cells associated with sickle cell anaemia are both reduced with co-existing alpha-thalassemia. Measurements of glycosylated hemoglobin levels as a function of cell density indicate that the accelerated increase in cell density, beyond normal cell ageing, in sickle cell anaemia is also reduced with alpha thalassemia. The patients with homozygous alpha-thalassemia and sickle cell disease have slightly lower levels of hemoglobin F than non-thalassemic patients. Examination of hemoglobin F production revealed that the proportion of hemoglobin F containing reticulocytes remained unchanged, as did the proportion of hemoglobin F in cells containing hemoglobin F (F cells). Preferential survival of F cells occurs in sickle cell anaemia, with or without alpha-thalassemia, and the slight difference in hemoglobin F levels appear to reflect differences in numbers of circulating F cells. Thus in sickle cell disease with co-existing alpha-thalassemia, the change in the erythrocyte density profile, possibly due to inhibition of polymerisation-related increases in cell density, explains the hematological improvement.(Summary)