Clinical phenotype of triplicated α-globin genes and heterozygosity for β0-thalassemia in Chinese subjects
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- Published online on: August 1, 2001 https://doi.org/10.3892/ijmm.8.2.171
- Pages: 171-175
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Abstract
The presence of extra copies of α-globin gene has been shown to worsen the degree of anemia in β-thalassemia heterozygotes. We describe the clinical phenotype of eight Chinese subjects with heterozygosity for both triplicated α-globin gene and a β0-thalassemia allele. They were identified through genotyping of β-thalassemia intermedia and major patients, and through community-based thalassemia screening program in Hong Kong. Standard molecular techniques were used in the determination of genotype. All subjects in this series showed five copies of α-globin genes (ααα/αα) in association with a β0-thalassemia allele. Although genotypically identical, six subjects showed a β-thalassemia intermedia phenotype while two were clinically indistinguishable from β-thalassemia minor, implying the presence of genetic modifying factors that remained undefined. Triplication of α-globin gene and heterozygosity for β0-thalassemia accounted for 15% of β-thalassemia intermedia patients at our locality and was associated with a mild clinical phenotype. This genotype was not found among β-thalassemia major patients. They presented in adulthood and were usually not transfusion dependent. When compared with simple β-thalassemia heterozygostes, they showed obvious red cell abnormalities (hypochromasia, anisopoikilocytosis, circulating normoblasts), lower hemoglobin (Hb) and higher HbF levels. The presence of triplicated α-globin genes should always be considered in apparent β-thalassemia carriers who were more symptomatic than expected, so that unnecessary investigations for the cause of anemia could be avoided. Finally, triplication of α-globin genes should be looked for in families with children affected by β-thalassemia intermedia in which only one parent showed a picture of β-thalassemia on Hb analysis.