Prenatal identification and genetic distribution of heterozygous HKαα/-SEA in a fetal umbilical blood sample and the family pedigree

Objective To identify one umbilical blood sample with abnonnal gap-PCR products of three bands of α2,-α3.7 and-SEA.further family pedigree were analyzed for the source of genetic variations,Methods One fetal umbilical blood sample was drawn from a woman of 24-weeks pregnancy.Gap-PCR for α-thalassemia was routinely conducted and abnornlal three bands of α2.-α3.7 and-SEA were observed.which could not be interpreted according to the kit manual and suspected as rare variation.With informed consen,DNA samples from the parents and grandparents were obtained for further study.Singleplex andnested PCR techniques were utilized to analyze the molecular characteristics of DNA samples from this fetus and its parents and grand-parents.Results Hematological phenotype study showed that fetal Hb Ban's was 7.6%,and its mother and maternal grandfather were both with typical α-thalassemia.while its father,grandfather and grandmother and maternal grandmother are without abnormal hematological change.Molecular study showed that fetal blood DNA was a heterozygosity for HKaa and-SEA.its father and grandfather are both HKαα/αα,its mother and maternal grandfather are both-SEA/aa,its grandmother and maternal grandmother are with both normal alleles of αα/αα.Then after genetic counseling the fetas was saved and iS a she baby now.Conclusion ThroUgh careful molecular tests one case of prenatal heterozygosity of HKαα/-SEA was identified,and the fetus is kept successfully through careful clinical counseling. Key words: Alpha-thalassemia; Prenatal diagnosis; Loss of heterozygosity; Pedigree