Prevalence and clinical phenotype of the triplicated α-globin genes and its ethnic and geographical distribution in Guizhou of China

BACKGROUND: α-thalassemia is relatively endemic in Guizhou province of southwestern China. To predict the clinical manifestations of α-globin gene aberration for genetic counseling, we examined the prevalence of the α-globin triplication and the genotype–phenotype correlation in this subpopulation METHODS: A cohort of 7644 subjects was selected from nine ethnicities covering four regions in Guizhou province of China. Peripheral blood was collected from each participant for routine blood testing and hemoglobin electrophoresis. PCR-DNA sequencing and Gap-PCR were used to identify the thalassemia gene mutations. Chi-square tests and one-way analysis of variance (ANOVA) were used to statistically analyze the data. RESULTS: We found that the frequency of α-globin triplication in Guizhou province was 0.772% (59/7644). Genotypically, the ααα(anti4.2)/αα accounted for 0.523% (40/7644), the ααα(anti3.7)/αα for 0.235% (18/7644), and the ααα(anti3.7)/–(SEA) for 0.013% (1/7644). The ααα(anti4.2)/αα is more prevalent than the ααα(anti3.7)/αα in Guizhou. In addition, the frequency of the HKαα/αα (that by GAP-PCR is like ααα(anti4.2)/-α(3.7)) was 0.235% (18/7644). Ethnically, the Tujia group presented the highest prevalence (2.47%) of α-globin triplication. Geographically, the highest frequency of the α-globin triplication was identified in Qiannan region (2.23%). Of the triplicated α-globin cases, 5 coinherited with heterozygote β-thalassemia and presented various clinical manifestations of anemia. CONCLUSIONS: These data will be used to update the Chinese triplicated α-globin thalassemia database and provide insights into the pathogenesis of thalassemia. These findings will be helpful for the diagnosis of thalassemia and future genetic counseling in those regions.