Genetic analysis of 2 cases of rare dominant β-thalassemia

Objective:To analyze and compare the gene mutations and clinical features of two cases of rare dominant β-thalassemia(β-thal)pediatric patients.Methods:Cases of thalassemia tested in the First Affiliated Hospital of Guangxi Medical University from January 2022 to December 2022 were screened.A blood cell analyzer was used for blood routine tests, and high performance liquid chromatography(HPLC)was used for hemoglobin(Hb) analysis.The α-and β-globin genes were analyzed by gap polymerase chain reaction (Gap-PCR), fluorescent PCR melting curve analysis (FCMA) and DNA sequencing.Results:2 cases of rare β-thal were detected.Case one, a 2-year-old boy, was the index case.He was found to be a heterozygote for CD28(CTG> CGG, HBB:c.86T> G) mutation of β-globin gene and had clinically moderate anemia.The results of his blood routine test showed the red blood cell count(RBC)3.42×10¹²/L, Hb level 73.00 g/L, mean corpuscular volume(MCV)69.00 fL, mean corpuscular hemoglobin (MCH) 21.30 pg, mean corpuscular hemoglobin concentration (MCHC)308.00 g/L, and red blood cell volume distribution width (RDW) 22.00%.Hb analysis showed Hb A₂ and Hb F were 4.8% and 7.6%, respectively.Case two, case one's sister, was also a heterozygote for CD28 (CTG> CGG)mutation and had clinically moderate anemia.The results of her blood routine test showed RBC 5.25×10¹²/L, Hb level 88.00 g/L, MCV 54.70 fL, MCH 16.80 pg, MCHC 307.00 g/L and RDW 17.20%.Hb analysis showed Hb A₂ and Hb F were 5.20% and 1.10%, respectively.Conclusion:The rare mutation of CD28(CTG> CGG)(HBB:c.86T> G)on β-globin gene leading to dominant β-thal is identified in the Chinese population for the first time and moderate anemia is present in the patient, suggesting that this type of mutation should be emphasized in clinical diagnosis, treatment and genetic counseling.