The Pedigree Analysis And Prenatal Diagnosis Of Hong Kongαα(HKαα)thalassemia

Objective:This study aims to describe the phenotype of Hong Kongαα(HKαα)thalassemia,to trace the law of inheritance of this genotype,to perform the prenatal diagnosis on the unborn fetus and offer the couple a relatively exact as well as efficient prenatal counseling.Methods : Peripheral blood of all of the participants(except the unborn fetus)was collected into EDTA-containing tubes.Whole blood cell counts and hemoglobin electrophoresis tests were performed on participants(except the unborn fetus).8ml of amniotic fluid was collected from the proband’s spouse.Genomic DNA was extracted from all individuals and fetal DNA was extracted from the amniotic fluid.Reverse dot blot was performed on all samples to detect the point mutation genotype of thalassemia.The single-tube multiplexpolymerase chain reaction(PCR)for four Chinese common deletional α thalassemia types(-α3.7,-α4.2,--SEA and--THAI)was performed to determine the deletional genotype of α thalassemia and the suspicious HKαα allele.PCR for the detection of αααanti4.2 allele was performed.The two round nested PCR was employed to determine the presence of the HKαα allele.Confirm the genotypes of all individuals and analyze the phenotypes.Results: The results indicated that five of the family members were positive for Hong Kongαα allele.One was diagnosed with the compound of HKαα/-α3.7 and β41-42M/βN.Two individuals with HKαα/--SEA,βN/βN.Another two individuals were positive for HKαα/-α4.2,βN/βN.The genotype of the unborn fetus was HKαα/-α4.2,βN/βN.Conclusions: Hong Kongαα,which is prone to be misdiagnosed,is a rare genotype of thalassemia.The combination of phenotype and the two-round nested PCR,which is a reliable laboratorial method,can help to avoid the possible underdiagnosis.