Analysis Of Gene Mutation Type And Frequency In Children With Thalassemia Aged 0-18 Years In Chengdu,Sichuan

Objective: Thalassemia refers to a hereditary hemolytic anemia in which protein synthesis is reduced or cannot be synthesized due to a defect in the globin gene.Severe thalassemia begins between three and twelve months after birth,and so far,the mainstays of treatment has been long-term regular blood transfusions and iron removal.Although children with thalassemia can survive for a long time and their disease burden and quality of life can be improved to some extent by this method,the infections and organ function damage associated with blood transfusion will also occur and cannot be ignored.Haematopoietic stemm cells(HSCT)have long been considered the main way to effectively deal with severe thalassemia,but this method is limited by difficulties in matching,high costs and safety issues,preventing its widespread clinical use in the treatment of patients with thalassemia.Therefore,pre-martial thalassemia screening,genetic counselling and antenatal examination can help reduce the probability of having children with thalassemia major.Sichuana Province has been identified as a high-incidence area of thalassemia,but there is a lack of related big data in the whole province,including Chengdu.In order to further understand the distribution of thalassemia genes in Chengdu,Sichuan Province,and to prevent and control the birth of children with thalassemia in Chengdu,this study analyzed the types and frequencies of thalassemia gene mutations in the age range of 0-18 years in Chengdu to understand the gene types and the specific proportion of children with the disease in the region and to provide a basis of decision making in intervention studies thereby reducing the birth rate of children with thalassemia in the region.Methods:(1)568 children with microcytic hypochromic anemia in the age group of 0-18 years,who were referred or transferred to Sichuan Provincial People’s Hospital from 11 districts(Jinjiang,Qingyang,Jinniu,Wuhou,Chenghua,Longquanyi,Qingbaijiang,Xindu,Wenjiang,Shuangliu and Pidu)and 9 counties(Jianyang,Dujiangyan,Pengzhou,Qionglai,Chongzhou,Jintang,Dayi,Pujiang and Xinjin)between September 2018 and July 2021,were selected;(2)Patients with abnormal blood routine screening were defined as positive for primary screening for thalassemia,i.e.hemoglobin level(Hb)< 110g/L,mean red blood cell volume(MCV)< 80 fl,mean red blood cell hemoglobin volume(MCH)< 27 pg;hemoglobin electrophoresis: when patients had hemoglobin A2(Hb A2)<2.5% and/or abnormal Hb bands such as Hb H,Hb Bart’s or Hb CS,they were defined as positive for α-thalassemia primary screening.When patients had hemoglobin A2(Hb A2)> 3.5% and/or haemoglobin F(Hb F)> 2%,they were defined as positive for β-thalassemia primary screening;(3)PCR-reverse dot blot hybridization was used to detectα-thalassemia of 3 deletions of-sea/α α,-α3.7/α α(right)and-α4.2/α α(left),and 3 non-deletions of αWS,αQS and αCS;17 kinds of β-thalassemia gene mutations were detected by PCR-RDB technology,including-28A→G,-29A→G,ATG→AGG,cd17A→T,-32C→A,βE,-30T→C,cd31(-C),cd122C→G,cd27-28(+C),cd41-42(-TCTT),5 ’UTR;+40-43(-AAAC),cd43 G → T,cd71-72(+A),IVS-1-1G→T,IVS-1-5G→C,IVS-2-654C→T,cd125T→C,and cd142T→C.Results:(1)Among the 568 children with positive result of thalassemia primary screening,356 cases were genetically detected,with an overall positive rate of 62.68%,including 140 cases of α-thalassemia(positive rate: 24.65%),202 cases of β-thalassemia(positive rate: 35.56%)and 14 cases of α-complexβ-thalassemia(positive rate: 2.46%);(2)Among the 140 cases of α-thalassemia,the gene mutation type was dominated by the genotypes of αα/--sea(79.29%),αα/-α3.7(7.86%),and-α3.7/--sea(7.14%),accounting for 94.29% of all types;(3)Among the 202 cases of β-thalassemia,there were 199 cases of simple heterozygotes,with the most common genotypes of cd17(A→T)(36.13%),cd41-42(-TCTT)(32.68%),and IVS-2-654(C→T)(20.79%),accounting for88.61% of all types,and 3 cases of double heterozygotes,and no pure heterozygotes of β-thalassemia were detected;(4)There were 14 α-complexβ-thalassemia patients identified,including 2 cd41-42(-TCTT)/-α3.7,2VS-2-654(C→T)/--sea,2 cd17(A→T)/-α3.7,and 2 cd41-42(-TCTT)/--sea genotypes.There was no gender difference between α-and β-thalassemia in Chengdu,but the prevalence of α combined with β-thalassemia was higher in males(P=0.003)Conclusions: The gene mutations of α-thalassemia in Chengdu are mainlyαα/--sea,αα/α3.7 and-α3.7/--sea genotypes;the genotypes of β-thalassaemia has more common in males than females.