[Phenotyping and genotyping studies in a family with the compound heterozygosity for a deletional delta beta-thalassemia and a beta-thalassemia].

OBJECTIVE: To investigate the relationship between genotype and phenotype of a deletional delta beta-thalassemia and explore an approach to rapid prenatal diagnosis for compound heterozygotes of this defect and a beta-thalassemia. METHODS: A total of ten members in a Chinese family who had a 5-year-old propositus with thalassemia major and requested prenatal diagnosis for the second pregnancy were investigated. For genotyping analysis, the deletional delta beta-thalassemia was characterized by gap-PCR method and beta-thalassemia mutations were defined by reverse dot blot(RDB). For phenotyping analysis, hematological data including the RBC indices, quantification of HbF and HbA2 by Hb electrophoresis and the ratio of globin chain Ggamma/(Ggamma+Agamma) analyzed by capillary electrophoresis (CE) were obtained. RESULTS: The propositus inherited her mother's delta beta-thalassemia gene mutation and her father's CD41-42(-CTTT) frameshift mutation. Of nine members in this family screened for this type of deletion, four were positive and the phenotype could be explained satisfactorily by genotype. The results of prenatal diagnosis showed that the fetus was normal and had no beta-globin gene defects in both chromosomes. CONCLUSION: This is the first time to have performed prenatal diagnosis in Chinese family at-risk of compound heterozygotes for beta-thalassemia and delta beta-thalassemia in mailand China. The strategy to analyze the disease presented here may be a valuable reference to the similar problem.