Beta-globin Gene Mutations in Turkish Children with Beta-Thalassemia: Results from a Single Center Study

INTRODUCTION: The beta thalassemias are common genetic disorders in Turkey and in this retrospective study our aim was to evaluate β-globin chain mutations and the phenotypic severity of β-thalassemia patients followed-up in our hospital, a tertiary center which serves patients from all regions of Turkey. MATERIALS AND METHODS: 106 pediatric patients were analysed for β-globin gene mutations by using DNA analysis. Patients were classified as having β-thalassemia major or β-thalassemia intermedia based on age at diagnosis, transfusion frequency and lowest hemoglobin concentration in between transfusions. RESULTS: There were 106 patients (52.8% female and 47.2% male) with a mean age of 11.2±5 years (1.6 – 22.3 years). Eighty-four (79.2%) patients had β-thalassemia major, whereas the remaining 22 patients (20.8%) were identified as having β-thalassemia intermedia. Overall, 18 different mutations were detected on 212 alleles. The most frequently encountered mutation was IVS I.110 (G>A) (35.3%), followed by Codon 8 del-AA (10.4%), IVS II.1 (G>A) (8%), IVS I.1 (G>A) (7.5%), Codon 39 (C>T) (7.1%) and Codon 5 (−CT) (6.6%), which made up 79.4% of observed mutations. According to present results, IVS I.110 (G>AA) was the most frequent mutation observed in this study, as in other results from Turkey. Evaluation of β-thalassemia mutations in 106 patients with 212 alleles, revealed the presence of homozygous mutation in 85 patients (80.2%) and compound heterozygous mutation in 21 patients (19.8%). The mutations detected in patients with homozygous mutation were IVS I.110 (G>A) (38.8%), Codon 8 del –AA (11.8%), IVS II.1 (G>A) (8.2%) and IVS I.1 (G>A) (8.2%). Observed mutations in the compound heterozygotes were Codon 39 (C>T)/Codon 41–42 (−CTTT) (14.3%), IVS I.110 (G>A)/Codon 39(C>T) (14.3%), IVS I.110 (G>A)/Codon 44(−C) (14.3%), and IVS II.745 (C>G)/5′UTR + 22 (G>A) (9.5%). CONCLUSION: Our hospital is a tertiary referral center that provides care to patients from all over the country, and thus the distribution of mutations observed in the current study is significant in term of representing that of the country as a whole.