The Spectrum of β-Thalassemia Mutations in Hatay, Turkey: Reporting Three New Mutations

Active spread of β-thalassemia beyond the thalassemia belt: A study on a Russian population

β-Thalassemia is a disease traditionally associated with thalassemia belt countries. Nonetheless, as global migration intensifies, β-thalassemia-causing variants spread far from their origin. We investigated this process to detect some patterns underlying its course. We analyzed β-thalassemia-causing variants and the origin of 676 unrelated participants in Moscow, the largest city of Russia, far away from the thalassemia belt. Our analyses revealed that modern Russia has one of the broadest spectra of thalassemia-causing variants: 46 different variants, including two novel β0 variants. Only a small proportion of the reported pathogenic variants likely originated in the resident subpopulation. Almost half of the variants that supposedly had emerged outside the Russian borders have already been assimilated by (were found in) the resident subpopulation. The primary modern source of immigration transferring thalassemia to a nonthalassemic part of Russia is the Caucasus region. We also found traces of ancient migration flows from non-Caucasus countries. Our data indicate that β-thalassemia-causing variants are actively spilling over into resident populations of countries outside thalassemia belt regions. Therefore, viewing thalassemia as a disease exclusive to specific ethnic groups creates a mind trap that can complicate the diagnosis.

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.

A National Registry of Thalassemia in Turkey: Demographic and Disease Characteristics of Patients, Achievements, and Challenges in Prevention

Objective:

The Turkish Society of Pediatric Hematology set up a National Hemoglobinopathy Registry to demonstrate the demographic and disease characteristics of patients and assess the efficacy of a hemoglobinopathy control program (HCP) over 10 years in Turkey.

Materials and Methods:

A total of 2046 patients from 27 thalassemia centers were registered, of which 1988 were eligible for analysis. This cohort mainly comprised patients with β-thalassemia major (n=1658, 83.4%) and intermedia (n=215, 10.8%).

Results:

The majority of patients were from the coastal areas of Turkey. The high number of patients in Southeastern Anatolia was due to that area having the highest rates of consanguineous marriage and fertility. The most common 11 mutations represented 90% of all β-thalassemia alleles and 47% of those were IVS1-110(G->A) mutations. The probability of undergoing splenectomy within the first 10 years of life was 20%, a rate unchanged since the 1980s. Iron chelators were administered as monotherapy regimens in 95% of patients and deferasirox was prescribed in 81.3% of those cases. Deferasirox administration was the highest (93.6%) in patients aged <10 years. Of the thalassemia major patients, 5.8% had match-related hemopoietic stem cell transplantation with a success rate of 77%. Cardiac disease was detected as a major cause of death and did not show a decreasing trend in 5-year cohorts since 1999.

Conclusion:

While the HCP has been implemented since 2003, the affected births have shown a consistent decrease only after 2009, being at lowest 34 cases per year. This program failure resulted from a lack of premarital screening in the majority of cases. Additional problems were unawareness of the risk and misinformation of the at-risk couples. In addition, prenatal diagnosis was either not offered to or was not accepted by the at-risk families. This study indicated that a continuous effort is needed for optimizing the management of thalassemia and the development of strategies is essential for further achievements in the HCP in Turkey.

Presence of the IVS-I-6-Mutated Allele in Beta-Thalassemia Major Patients Correlates with Extramedullary Hematopoiesis Incidence

Extramedullary hematopoiesis (EMH) results from the extension of hematopoietic tissue beyond the confines of the bones. Since the initiation of regular transfusion programs from an early age for all thalassemia major (ΤΜ) patients, EMH has not been considered a clinical issue anymore. The present study aims to record the prevalence of EMH in chronically transfused ΤΜ patients followed at our institution and to investigate possible risk factors associated with its occurrence. The project was designed as a retrospective, nonexperimental, descriptive, exploratory study. In total, the study enrolled 104 patients. EMH was revealed in 15/104 (14%) patients. The presence of intravening sequence (IVS)-I-6 was significantly related with the development of EMH (p < 0.05). No other demographic or biological factor studied was found to be related with the presence of EMH. The study stresses a profound incidence of asymptomatic EMH in a solid group of well-transfused ΤΜ patients. Given the high incidence of the IVS-I-6 allele in the Mediterranean and Middle Eastern region, high-quality, prospective, multicenter studies could confirm the association of EMH occurrence with the presence of the IVS-I-6 mutation and further evaluate the exact role of this mutation in the EMH process.

Hemoglobinopathies in the Çukurova Region and Neighboring Provinces

To contribute to the creation of a mutation map of the region, we aimed to determine the mutation spectrum of thalassemias and abnormal hemoglobins (Hbs) in the Çukurova region and surrounding provinces. In this study, a total of 8135 samples from Adana, Hatay, Mersin, Konya and Kayseri provinces between 1993 and 2014 were analyzed. Complete blood cell (CBC) counts and Hb typing were carried out using automatic cell counters, cellulose acetate membrane electrophoresis and high performance liquid chromatography (HPLC), respectively. For the molecular analyses, genomic DNA was extracted using both manual and automated DNA extraction devices. Determination of Hb mutations were done by microarray, restriction fragment length polymorphism (RFLP), amplification refractory mutation system (ARMS) and gap-polymerase chain reaction (gap-PCR) methodologies. Samples were analyzed for abnormal Hb and thalassemia mutations. Out of 8135 samples, 1382 were observed to be carrying Hb mutations. It was identified that 826 mutation carriers included abnormal Hbs with a frequency of 59.7%, 416 carriers included β-thalassemia (β-thal) mutations with a frequency of 30.7% and 136 carriers included α-thalassemia (α-thal) mutations with a frequency of 9.9%. In this study, the most frequently observed abnormal Hb in the region was Hb S [β6(A3)Glu→Val (GTG > GAG), HBB: c.20T > A], whereas the most commonly observed mutations were the IVS-I-110 (G > A) (HBB: c.93-21G > A) point mutation in β-thal and the 3.7 kb deletion in α-thal.