Mild thalassemia: the result of interactions of alpha and beta thalassemia genes

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RESUMO

Homozygous thalassemia is due to inherited unbalanced synthesis of the α- or β-chains of hemoglobin. Clinical severity may be in part related to the extent of α:β imbalance. Two families are presented that illustrate this concept. Thalassemia in these individuals was evaluated by clinical and genetic criteria. The relative rates of α- and β-chain synthesis in their reticulocytes were estimated by the extent of incorporation of 1-leucine—U-14C into the chains. Unusual combinations of clinical and hematological data and biosynthetic ratios were obtained in certain individuals which indicated the presence of combinations of α- and β-thalassemia genes. The propositus of the first family had mild Cooley's anemia and was believed to have one α- as well as two β-thalassemia genes. Presumably the α-thalassemia gene interfered with α-chain production which lead to less accumulation of α-chains and a reduced rate of intramedullary and peripheral hemolysis. In the second family two individuals were believed to have an α-thalassemia, a “silent carrier,” and a β-thalassemia gene. Despite the fact that they appeared to have the genotype of hemoglobin H disease, their cells contained no hemoglobin H and had a normal lifespan presumably because excess β-chain production was inhibited by the β-thalessemia gene. These family studies suggest that the α:β imbalance observed in thalassemia may be favorably influenced by combinations of α- and β-thalassemia genes.

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