β-Thalassemia gene mutations in Antalya, Turkey: results from a single centre study

The Spectrum of Beta-Thalassemia Mutations in Syrian Refugees and Turkish Citizens

Introduction and objectives

Neighboring the border between Turkey and Syria, Sanliurfa is one of the Turkish provinces with the highest number of Syrian refugees in our country. We aimed to find out the spectrum of beta-globin gene mutations in adult Turkish citizens and Syrian refugees with beta-thalassemia major.

Results

Of the participants, 35 patients (70%) were Turkish citizens and 15 patients (30%) were Syrian. The most common mutation in Turkish patients was found to be IVS-I-110 (G>A) with a frequency of 28.8%, followed by IVS-I-6 (T>C) with a frequency of 15.5%. Other common mutations were IVS-I-1 (G>A) and codon 39 (C>T) with frequencies of 11.1%. These four mutations accounted for 65.5% of all mutations in the Turkish cohort. The most common mutations in Syrian refugee patients were IVS-I-1 (G>A), IVS-II-1 (G>A), IVS-I-5 (G>C), and codon 5 (-CT), all with a frequency of 15.7%, accounting for 62.8% of all mutations in the Syrian patients. In the analysis, codon 5 (-CT) mutation (15.7% vs 0%, p=0.023) was found significantly higher in Syrian refugees compared to Turkish citizens.

Discussion and conclusions

A wide spectrum of mutations was detected in beta-thalassemia major patients living in the Sanliurfa region. Mutational profiles in Turkish and Syrian patients were found to be significantly different from each other. Because marriages between Syrian refugees and Turkish citizens are increasing in our region, the genetic findings and the mutational profiles in Turkish and Syrian patients obtained in this study are thought to become useful for future prenatal molecular diagnostic tests.

The Spectrum of β-Thalassemia Mutations in the Population Migration in Lebanon: A 6-Year Retrospective Study

β-Thalassemia (β-thal) is highly prevalent among the Mediterranean populations. In Lebanon, the carrier rate of the disease is estimated to be around 2.0-3.0%. In this retrospective study, we determined the spectrum of β-thal mutations in a total of 170 individuals from a sample of 140 Lebanese, Iraqi and Syrian refugee families in Lebanon, over a period from 2012 to 2018. Twenty-eight different β-globin gene mutations were identified. The most prevalent mutations were IVS-I-110 (G>A) (HBB: c.93-21G>A), IVS-II-1 (G>A) (HBB: c.315+1G>A), IVS-I-6 (T>C) (HBB: c.92+6T>C) and IVS-I-1 (G>A) (HBB: c.92+1G>A), accounting for the majority of mutations found in HBB mutations analysed in 250 alleles. Ten different β-globin gene mutations that were not previously described in Lebanon were identified in our study. These mutations include the IVS-II-848 (C>A) (HBB: c.316-3C>A), codons 9/10 (+T) (HBB: c.30_31insT), codon 15 (-T) (HBB: c.46delT), -86 (C>G) (HBB: c.-136C>G), Cap +22 (G>A) (HBB: c.-29G>A), -28 (A>C) (HBB: c.-78A>C), codon 7 (GAG>TAG) (HBB: c.22G>T), codon 26 (GAG>TAG) (HBB: c.79G>T), codons 41/42 (-TTCT) (HBB: c.126_129delCTTT), and codons 82/83 (-G) (HBB: c.250delG). Of these, six mutations [codons 9/10, codon 15 (-T), -86, codon 7, codon 26, codons 82/83) were identified in Lebanese samples only; one mutation (IVS-II-848) was identified in both Lebanese and Iraqis; and three mutations (Cap +22, -28, codons 41/42) were identified in Iraqi samples only. Further studies will help better delineate the spectrum of β-thal mutations among different ethnic groups, and provide crucial prevention strategies.

Presentation of two new mutations in the 3'untranslated region of the β-globin gene and evaluating the molecular spectrum of thalassemia mutations in the Mediterranean region of Turkey

Thalassemia is a common genetic disorder. We aimed to present thalassemia mutation data that covers a period of 7 years from the Mediterranean region of Turkey by comparing with hemoglobin indices and to contribute to prenatal diagnosis and genetic counseling studies which should be decided very quickly. In this study, in which a retrospective archive was scanned, the cases were first grouped as α and β thalassemia, and then β thalassemia mutations were examined in a total of 5 groups as UTR-Pro, Codon, IVS, β⁰, and β⁺. We have reached the family of the proband that analyzed their Hb indices and genetic mutation. All mutations were statistically compared with Hb indices, HbF, and HbA₂. We have identified two new β thalassemia mutations that have the feature of not being defined previously [HBB:C*62 A>G. (3'UTR+1536 A>G) and HBB:C*1 G>A (3'UTR+1475 G>A)]. The most commonly encountered 23 mutations account for 74.7% of all mutations which is unlike the literature. In the β thalassemia group, 73 different mutations were detected. The most common β thalassemia mutation was HBB: c.93-21 G>A (IVS I-110 G>A) with a frequency of 19.72%. A statistically significant difference was found when comparing the mutation groups with Hb indices. We think that it may be useful to evaluate the mutations we have newly identified too together with the Hb indices especially in evaluating the carriers of thalassemia and it will contribute to prenatal diagnosis and genetic counseling studies which should be decided very quickly.

Missed Diagnosis of β-Thalassemia Trait in Premarital Screening Due to Accompanying HbA2-Yialousa (HBD: c.82G>T)

The diagnosis of β-thalassemia (β-thal) trait is usually based on an elevated HbA2 fraction (3.5% to 8%). Co-inheritance of a δ-globin variant along with β-globin gene defects can interfere with the diagnosis of β-thal trait by causing normal HbA2 levels. In this report, we present an infant with β-thal major whose mother's β-thal trait was missed twice before due to an accompanying δ-globin mutation (HbA2-Yialousa; HBD: c.82G>T), resulting in a borderline HbA2 level. In an individual with microcytosis and hypochromia but an apparently normal HbA2 level, compound heterozygosity for a δ-globin mutation and a β-thal mutation should be remembered in the differential diagnosis.

The Spectrum of β-Thalassemia Mutations in Siirt Province, Southeastern Turkey

β-Thalassemia (β-thal) is the most common hereditary genetic blood disorder. The aims of this study were: (i) to determine the mutation types and the frequency of these mutations in β-thal patients to obtain the ethnic origins of the population in Siirt Province; (ii) to evaluate the pathogenicity of these mutations by performing in silico analysis; (iii) to reveal the genotype-phenotype correlation by comparing the clinical manifestation of our patients to the specific mutations in this population. This study included 34 patients (18 males and 16 females) with a mean age of 9.1 ± 3.6 years (range 3-16 years). All mutations were determined using sequence analysis methods, and the mutations were analyzed using bioinformatics tools. Thirteen different mutations were detected in the patients: IVI-I-110 (G>A) (HBB: c.93-21G>A) (38.9%); IVS-II-1 (G>A) (HBB: c.315_1G>A) (11.1%); -30 (T>A) (HBB: c.-80T>A) (9.25%) and IVS-I-1 (G>A) (HBB: c.92 + 1G>A) (9.25%), were the most common, and these mutations constituted 68.5% of the cases. Missense codon 6 (A>T) (HBB: c.20A>T) was not pathogenic; however, all the intronic mutations (IVS-I-1, IVS-I-110, IVS-II-1) and frameshift mutations [codon 44 (-C) (HBB: c.135delC) and codons 36/37 (-T) (HBB: c.112delT)] resulted in disease. These mutations can be used to determine the ethnic origin of the Siirt population and, in affected pregnant women, to develop prenatal strategies. A fatal phenotype can be identified by in silico analysis; however, mutations that are unknown prior to marriage, pregnancy, and childbirth or new mutations can be less accurately identified.