Exploration On Occurrence Mechanism And Genotype Identification For Two Rare Cases Of Thalassemia

Background and objectivesHb Bart's hydrops fetalis syndrome(BHFS)patient results from deletion of all four ?-globin genes leading to the defect of ?-globin synthesis and excess ?-like globin chain aggregates into tetramer,which is termed Hb Bart's(?4)and HbH(p4).Both ?4 and ?4 cannot release oxygen in hypoxic tissue due to its extremely high oxygen affinity,which can result in restriction of growth and hydrops fetalis in the middle of pregnancy.The survivor of BHFS patient without intrauterine intervention is rarely reported.In this study,we reported a survivors of BHFS patient without intrauterine intervention and explored its mechanism,which could provide a new perspective for the study of BHFS.Materials and methods1.Subject:The proband was 1-year-old boy from Zhaoqing,Guangdong province and were diagnosed with BHFS patient.2.Methods:All members'peripheral blood samples were collected,and hematological parameters were analyzed.The genes of a and ? globin were detected by routine techniques.The PCR amplification in a-globin gene and MLPA were used to indentify the probands' genetype.The expression levels of globin gene were analyzed by fluorescent quantitative technology.The proband's hair follicle and buccal mucosa sample were obtained,and the ratio,source and genetype of this chimera were analyzed by PCR-STR,SNP analysis and fluorescent quantitative technology.ResultsThe result of Gap-PCR showed the proband existed the gene of HBA2 and her parent was--SEA carrier.But the ?-globin gene exists in proband by detection of PCR amplification in ?-globin gene and MLPA.Analysis of PCR-STR and SNP indicated the chimeric ratio in proband's blood,follicle and buccal mucosa sample was 5.2±0.8%,19.5±1.0%and 6.7±0.3%respectively which its genetype was--SEA/aa and the ?-globin gene derived from his mother.The result of fluorescent quantitative technology indicated the ratio of this genetype in proband's blood,follicle and buccal mucosa sample was 2.6%,8.9%and 3.6%respectively,and the expression of?-globin gene was 3.2%,which was consistent with analysis of PCR-STR and SNP.ConclusionIn this study,the survivors of BHFS patient without intrauterine intervention is better than the others in uterus due to the chimera of--SEA/?? genotypic cells,which will provide a new perspective for the study of BHFS.