Hemoglobinopathies in Yugoslavia: an update

The Relevance of β-Thalassemia Heterozygosity in Pediatric Clinical Practice: Croatian Experience

(1) Background: Thalassemia syndromes are common monogenic disorders that represent a significant global health issue. No systematic epidemiological or molecular investigations on thalassemias in the Croatian population have been reported to date. (2) Methods: This prospective study included 70 children with a presumptive diagnosis of thalassemia and their 42 first-degree relatives. Molecular characterization was performed using direct sequencing and gap-PCR methods. (3) Results: We identified 46 (30 children and 16 first-degree relatives) β-thalassemia heterozygous carriers from 24 unrelated families, carrying eight different mutations and one hemoglobin variant. Five variants account for approximately 85% of all affected β-globin alleles: Hb Lepore-Boston-Washington (32.6%), HBB:c.93-21G>A (19.6%), HBB:c.315+1G>A (13.1%), HBB:c.92+1G>A (10.9%), and HBB:c.92+6T>C (8.7%) variants. (4) Conclusions: β-thalassemia carriers need more detailed genetic profiling since genetic modifiers can significantly impact their phenotype. Our study provides important new insights into the relevance of β-thalassemia heterozygosity in pediatric clinical practice.

Thalassemias: From gene to therapy

Thalassemias (α, β, γ, δ, δβ, and εγδβ) are the most common genetic disorders worldwide and constitute a heterogeneous group of hereditary diseases characterized by the deficient synthesis of one or more hemoglobin (Hb) chain(s). This leads to the accumulation of unstable non-thalassemic Hb chains, which precipitate and cause intramedullary destruction of erythroid precursors and premature lysis of red blood cells (RBC) in the peripheral blood. Non-thalassemic Hbs display high oxygen affinity and no cooperativity. Thalassemias result from many different genetic and molecular defects leading to either severe or clinically silent hematologic phenotypes. Thalassemias α and β are particularly diffused in the regions spanning from the Mediterranean basin through the Middle East, Indian subcontinent, Burma, Southeast Asia, Melanesia, and the Pacific Islands, whereas δβ-thalassemia is prevalent in some Mediterranean regions including Italy, Greece, and Turkey. Although in the world thalassemia and malaria areas overlap apparently, the RBC protection against malaria parasites is openly debated. Here, we provide an overview of the historical, geographic, genetic, structural, and molecular pathophysiological aspects of thalassemias. Moreover, attention has been paid to molecular and epigenetic pathways regulating globin gene expression and globin switching. Challenges of conventional standard treatments, including RBC transfusions and iron chelation therapy, splenectomy and hematopoietic stem cell transplantation from normal donors are reported. Finally, the progress made by rapidly evolving fields of gene therapy and gene editing strategies, already in pre-clinical and clinical evaluation, and future challenges as novel curative treatments for thalassemia are discussed.

A Case of a 15-Month-Old With Periorbital Edema and Severe Anemia

This is the case of a previously healthy 15-month-old girl who initially presented to her primary pediatrician with a 2-week history of intermittent periorbital edema. The edema had improved by the time of the visit, and a urine specimen was unable to be obtained in the clinic. A routine fingerstick demonstrated anemia to 8.8 mg/dL, so the patient was started on ferrous sulfate. She then returned to the emergency department 1 month later with severe periorbital edema and pallor but no other significant symptoms. On physical examination, she was tachycardic with striking periorbital edema and an otherwise normal physical examination. She was noted to have a severe microcytic anemia (hemoglobin of 3.9 mg/dL and mean corpuscular volume of 53.1 fL) and hypoalbuminemia (albumin of 1.9 g/dL and total protein of 3.3 g/dL). The remainder of her electrolytes and liver function test results were within normal limits. A urinalysis was sent, which was negative for protein. Our panel of experts reviews her case to determine a unifying diagnosis for both her severe anemia and her hypoalbuminemia.

Comparison of Enzymatic Assay for HBA1C Measurement (Abbott Architect) With Capillary Electrophoresis (Sebia Minicap Flex Piercing Analyser)

Objective

To compare the analytical performances of the enzymatic method (EM) and capillary electrophoresis (CE) for hemoglobin A1c (HbA1c) measurement.

Methods

Imprecision, carryover, stability, linearity, method comparison, and interferences were evaluated for HbA1c via EM (Abbott Laboratories, Inc) and CE (Sebia).

Results

Both methods have shown overall within-laboratory imprecision of less than 3% for International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) units (<2% National Glycohemoglobin Standardization Program [NGSP] units). Carryover effects were within acceptable criteria. The linearity of both methods has proven to be excellent (R2 = 0.999). Significant proportional and constant difference were found for EM, compared with CE, but were not clinically relevant (<5 mmol/mol; NGSP <0.5%). At the clinically relevant HbA1c concentration, stability observed with both methods was acceptable (bias, <3%). Triglyceride levels of 8.11 mmol per L or greater showed to interfere with EM and fetal hemoglobin (HbF) of 10.6% or greater with CE.

Conclusion

The enzymatic method proved to be comparable to the CE method in analytical performances; however, certain interferences can influence the measurements of each method.

Genotype-phenotype Correlation of β-Thalassemia in Croatian Patients: A Specific HBB Gene Mutations

An analysis of genotype-phenotype correlation was performed for 14 patients with beta-thalassemia who had been registered in Referral Centre for hematology and oncology of the University Hospital Centre, Zagreb, Croatia. HBB gene mutations were determined using a gene-specific Q5 High-Fidelity PCR analysis with direct DNA sequencing of amplified transcripts. Mahidol score index used for classification of thalassemia severity was found to be low for all the patients enrolled in the study, indicating a mild β-thalassemia phenotype with no signs of disease progression. Most of the patients have already described gene mutations: IVS-II-666 C>T (HBB:c.316-185C>T) and IVS-II-16 G>C (HBB:c.315+16G>C). Each of the aforementioned mutations was found in (11/14; 78,57%) and (10/14; 71,43%) of our patients, respectively. Recently published HBB:c.9T>C mutation was found in 8 of 14 (57,14%) in our study group. IVSII-74 T>G (HBB:c.315+74T>G) is a worldwide mutation found in 6 of 14 (42.86%) of our patients. All these mutations occur among Croatian children with no obvious Indian/Near Eastern/Iranian ancestry. We also identified 7 de novo mutations (c.316-135het_dupT, c.316-133A>G, c.93-54G>A, c.316-68_316-67het_insCGG, c.316-342delA, c.316-312delT, c.316-209delT) of mild severity phenotype according to Mahidol classification score index. We did not find children or adults with thalassemia major severity phenotype.

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.

β-Thalassemia Haplotypes in Romania in the Context of Genetic Mixing in the Mediterranean Area

The purpose of this meta-study was to investigate β-thalassemia (β-thal) mutations and their chromosomal background in order to highlight the origin and spread of thalassemia alleles in the European and Mediterranean areas. Screening of more than 100 new Romanian β-thal alleles was also conducted. The results suggest an ancient introduction of mutations at codon 39 (C > T) (HBB: c.118C > T) and IVS-I-6 (T > C) (HBB: c.92 + 6T > C) in Romania. A comparative study was performed based on restriction fragment length polymorphism (RFLP) haplotypes associated with β-thal mutations in Romania and in Mediterranean countries. Each common β-thal allele from different populations exhibits a high degree of haplotype similarity, a sign of a clear unicentric origin for the IVS-I-110 (G > A) (HBB: c.93-21G > A), IVS-I-6, IVS-II-745 (C > G) (HBB: c.316-106C > G) and codon 39 mutations (the 17a [+ - - - - + +], 13c [ - + + - - - +], 17c [ + - - - - - +] and 14a [- + + - + + + ] ancestral RFLP background, respectively), followed by recurrent recombination events. This study also showed that geographic distances played a major role in shaping the spread of the predominant β-thal alleles, whereas no genetic boundaries were detected between broad groups of populations living in the Middle East, Europe and North Africa. The analyses revealed some discrepancies concerning Morocco and Serbia, which suggest some peculiar genetic flows. Marked variations in β(A) were observed between Southeast Asia and the Mediterranean, whereas a relative genetic homogeneity was found around the Mediterranean Basin. This homogeneity is undoubtedly the result of the high level of specific historic human migrations that occurred in this area.

Screening for common β-globin gene cluster deletions in Chinese individuals with increased hemoglobin F

INTRODUCTION

The aim of this study was to determine the prevalence of β-globin gene cluster deletions in individuals with increased Hb F levels in a Chinese population.

METHODS

Subjects with HbF levels ≥ 10% were selected for further investigation. Gap-PCR was used to screen for three common β-globin gene cluster deletions: Chinese ((A) γδβ)(0)-thalassemia, Southeast Asian (SEA) deletion and Hb Lepore. Multiplex ligation-dependent probe amplification (MLPA) was used to analyze dosage changes of the β-globin gene cluster for those not associated with one of the three common deletions.

RESULTS

One hundred and thirty-one individuals had an increased Hb F level; among these, 51 (38.9%) were showed to have Chinese ((A) γδβ)(0)-thalassemia (n = 37) or SEA deletion (n = 14). A single case of Hb Lepore-Boston-Washington was detected. MLPA only detected 2 deletions in three cases of the remaining 80 patients. Gap-PCR confirmed that they included a 1357 bp β-globin gene deletion (NG_000007.3:g.69997_71353del1357) in one case and a HBG2-HBG1 fusion gene consisting of exons 1 and 2 of HBG2 ((G) γ-globin gene) and exon 3 of HBG1 ((A)γ-globin gene) (HBG2:c.315 + 573_HBG1: c.315 + 572del) in two cases.

CONCLUSION

The Chinese ((A) γδβ)(0)-thalassemia and SEA deletion are the most common large deletions of β-globin gene cluster in Chinese. Gap-PCR for the detection of these two deletions should be used in thalassemia screening program in China where the incidence of β-thalassemia is high.

Thalassemias and Other Hemoglobinopathies in the Republic of Macedonia

This paper summarizes the results on the epidemiology and molecular basis of thalassemias and other hemoglobinopathies in the Republic of Macedonia. Over the past 40 years, population surveys of more than 22,000 participants (school children and workers) from all over the country, have shown that the average incidence of beta-thalassemia (thal) trait is 2.6%, ranging from less than 1% in the northeast to 10% in the south. The frequency of deltabeta-thal is 0.2%, while the frequency of the Swiss type of hereditary persistence of fetal hemoglobin (HPFH) is 0.3%. Screening of 9,619 newborns has shown that the frequency of alpha-thal trait is 1.5%, of which alpha-thal-2 is 1.45% and alpha-thal-1 is 0.05%. The molecular basis of the different forms of beta-thal and other hemoglobinopathies has been completely defined. Among the Macedonians, over 450 beta-thal chromosomes have been studied. Fifteen different beta-thal mutations have been detected, four of which [IVS-I-110 (G-->A), IVS-I-6 (T-->C), IVS-I-1 (G-->A), codon 39 (C-->T)] account for 85% of all beta-thal chromosomes. Among the Albanians, 48 beta-thal chromosomes have been studied. Eight different mutations have been detected, four of which [codon 39, -30 (T-->A), IVS-I-110, IVS-I-1] account for 85% of all beta-thal chromosomes. Four new mutations [-101 (C-->A), -87 (C-->G), -30, polyadenylation signal (poly A) (AATAAA-->AATGAA)] have been characterized. Molecular analyses of DNA from over 20 unrelated cases with deltabeta-thal have shown that this condition is caused by a 13 kb deletion (Sicilian type); in two families a deletion of 18 to 23 kb (Macedonian type of deltabeta-thal) was discovered. Molecular analyses of alpha-thal in the Republic of Macedonia have shown the following types of molecular defects: 20.5 kb deletion, 17.5 kb deletion, 3.7 kb deletion, poly A mutation (AATAAA-->AATGAA), and Hb Icaria [alpha142, Term-->Lys, TAA-->AAA (alpha2)]. The incidence of abnormal hemoglobins (Hbs) in the Republic of Macedonia is 0.4%. Three different alpha chain variants among 10 families, seven different beta chain variants among 33 families, two gamma chain variants in two newborns, one variant with an extended alpha chain, and Hb Lepore among 105 families, have been observed. Structural analysis of numerous cases with Hb Lepore showed that the variant was of the Washington-Boston type.

Rare occurrence of Hb Lepore-Baltimore in African Americans: molecular characteristics and variations of Hb Lepores

Hb Lepore is the hybrid hemoglobin (Hb) composed of two alpha-globin chains and two deltabeta hybrid chains and is associated with the clinical findings of thalassemia minor in its heterozygous form. Hb Lepore can be found in many ethnic groups, commonly in southern European countries, but rarely in African Americans. The first Hb Lepore case in an African-American individual was named Hb Lepore-The Bronx (Hb Lepore-Boston). Hb Lepore-Washington-Boston and Hb Lepore-Baltimore with a breakpoint of (delta50Ser/beta86Ala) were later reported. In this paper, we describe an Hb Lepore-Baltimore (delta68Leu/beta84Thr) deltabeta-fusion gene with a different breakpoint detected for the first time in an African-American female. We have used state-of-the-art technology, combining protein- and DNA-based methods, in the analysis of the hybrid hemoglobin and discuss its molecular characteristics.

Thalassemias and Other Hemoglobinopathies in Former Yugoslavia

This review summarizes our results on the epidemiology and molecular basis of thalassemias and other hemoglobinopathies in the republics and provinces of the Former Yugoslavia. Over the past 40 years, surveys of more than 37,000 school children and more than 1,600 adults, from all over Former Yugoslavia, except Slovenia, have shown an average incidence of β-thalassemia (β-thal) trait of 1.2%, ranging from 2.9% in the south (Macedonia) to 0.8% in the northwest (Croatia). The frequency of δβ-thal was 0.2%, while that of Swiss type hereditary persistence of fetal hemoglobin (HPFH) was 0.4%. Screening of 12,680 newborns has shown that the frequency of α-thal trait was 1.5%. The molecular basis of the thalassemias in the populations of Former Yugoslavia has been completely defined. More than 700 β-thal chromosomes have been studied and their molecular defect was determined. In the Macedonian population, 16 different β-thal mutations were detected, four of which (IVS-I-110, G→A; IVS-I-6, T>C; IVS-I-1, G>A and codon 39, C>T) accounted for 85% of all β-thal chromosomes. In the Croatian population, 18 different β-thal alleles were detected. Four new mutations [nucleotide (nt) -87, C>A; IVS-II-850, G>C; initiation codon mutation T>C; polyadenylation signal (poly A), AATAAA>AATGAA)] and one new deletion (1605 bp), were characterized. Molecular analyses of DNA from over 50 unrelated cases with δβ-thal have shown that this condition was mainly caused by a 13 kb deletion (Sicilian type); in one family, a deletion of >18 to 23 kb (Macedonian-Turkish type), and in another, a deletion of 148 kb (Yugoslavian type of εγδβ-thal) of the β-globin gene complex, were discovered. Molecular analyses of α-thal from Former Yugoslavia revealed the following defects: the -20.5, -17.5 and -3.7 kb deletions, a 5 nt deletion, and Hb Icaria [α142, Term→Lys (TAA>TCA in α2)]. The incidence of abnormal hemoglobins (Hbs) in Former Yugoslavia was 0.3%. Five different α chain variants in 16 families, 16 different β chain variants in 61 families, one δ chain variant in one family, two types of Hb Lepore in 122 families and two γ chain variants, have been characterized.

Molecular basis of thalassemia syndromes in Serbia and Montenegro

This study reports the molecular characterization of thalassemia syndromes in Serbian and Montenegrin populations. We identified eight beta-thalassemia mutations [codon 39 (C-->T), IVS-I-110 (G-->A), IVS-II-745 (C-->G), codon 44 (-C), -87 (C-->G), IVS-II-1 (G-->A), IVS-I-6 (T-->C), IVS I-1 (G-->A)] in 70 members of 29 families using polymerase chain reaction, reverse dot blot, amplification refractory mutation system and direct sequencing analysis. Hemoglobin (Hb) Lepore was found to be the most common cause of the thalassemia phenotype. Hb Sabine and alpha-thalassemia were detected as well. We also studied beta-globin gene cluster haplotypes and their association with the most common mutations. A novel haplotype associated with the Hb Lepore gene was identified. The results presented herein allowed the implementation of a prenatal diagnosis program in Serbia and Montenegro.

β -thalassaemia-87 C→G: relationship of the Hb F modulation and polymorphisms in compound heterozygous patients

A clinical, haematological, biochemical and molecular study was carried out in 17 patients affected with thalassaemia intermedia, who were compound heterozygotes for the beta-thalassaemia mutation beta-87 C-->G to determine the genetic basis of their clinical heterogeneity. The beta-87 was found associated with haplotype VIII (beta-87/VIII) or V (beta-87/V). The 10 patients with the beta-87/VIII showed milder clinical conditions, with significantly higher levels of haemoglobin (Hb) (9.8 +/- 1.1 g/dl vs. 8.5 +/- 1.3 g/dl) and fetal haemoglobin (Hb F) (6.2 +/- 1.5 g/dl vs. 2.6 +/- 1.5 g/dl; P = 0.0034) and higher synthesis of (G)gamma ((G)gamma/(Total)gamma 69.4 +/- 2.6% vs. 42.8 +/- 16.2%; P = 0.0042) than the seven patients with the beta-87/V. The beta-87/VIII showed a configuration of rare polymorphisms in the 5' sub-haplotype, which have been reported to exert an increasing effect on Hb F. They were "T"-158 (G)gamma-globin gene, T-A-G in pre-(G)gamma framework, (TG)(11)(CG)(3) in the (G)gamma-IVS2, (AT)(9)N(12)(AT)(10) in LCR-HS2; in contrast, the haplotype V had, respectively, "C", T-G-A (TG)(19)(CG)(2)CACG in the (G)gamma-IVS2, and (AT)(10)N(12)(AT)(11). In all patients the beta-87 was associated with the (AT)(9)T(5) motif 5' beta-globin gene with increased affinity for the BP-1 protein, and with the (TG)(13) in the (A)gamma-IVS2. The high increase of the Hb F, mostly of the (G)gamma-type, strongly suggests the hypothesis that the 'T'-158 (G)gamma plays a principal role and that the other polymorphisms could exert a cooperative role in the modulation of Hb F in patients with erythropoietic stress.

Agamma-haplotypes: a new group of genetic markers for thalassemic mutations inside the 5' regulatory region of the human Agamma-globin gene

This study illustrates the relationship between a group of nucleotide variations within the 5' regulatory region of the Agamma-globin gene [Agamma-588 A-->G, Agamma-499 T-->A and the 4-bp deletion (Agamma-225 to -222 AGCA)] and the spectrum of delta- and beta-thalassemia mutations in the Hellenic population. These sequence variations, screened by means of denaturing gradient gel electrophoresis, form four separate frameworks (Agamma-haplotypes), each one of which was found to be linked in cis with certain delta- and beta-thalassemia mutations found in the Hellenic population. In addition, two novel base substitutions inside the 5' regulatory region of the Agamma-globin gene (Agamma-521 C-->A and Ay-500 C-->T) were identified during this study, which together with Agamma-haplotypes seem to be silent polymorphisms during adult life, as indicated by transient expression assays. Our data show that Agamma-haplotypes represent genetic markers for the spectrum of thalassemic mutations, found in the Hellenic population and can constitute an important genetic repository upon which mutations leading to thalassemia and hemoglobinopathies occurred.

The population genetics of the haemoglobinopathies

The haemoglobinopathies are the commonest single-gene disorders known, almost certainly because of the protection they provide against malaria, as attested by a number of observations. The geographical distributions of malaria and haemoglobinopathies largely overlap, and microepidemiological surveys confirm the close relationship between them. For two of the commonest disorders, haemoglobin S and alpha(+)-thalassaemia, there is also good clinical evidence for protection against malaria morbidity. However, not all the evidence appears to support this view. In some parts of the world malaria and haemoglobinopathies are not, and never have been, coexistent. It is also difficult to explain why the majority of haemoglobinopathies appear to be recent mutations and are regionally specific. Here we argue that these apparent inconsistencies in the malaria hypothesis are the result of processes such as genetic drift and migration and of demographic changes that have occurred during the past 10,000 years. When these factors are taken into account, selection by malaria remains the force responsible for the prevalence of the haemoglobinopathies.

Association of Hb S/Hb lepore and delta beta-thalassemia/Hb lepore in Sicilian patients: review of the presence of Hb lepore in Sicily

The hemoglobin (Hb) lepore-Boston is a beta-globin structural variant, produced in a reduced amount and formed from the fusion of N-terminus delta-(residues 1-87) and C-terminus beta-chains (residues 116-146). This type of fusion protein is quite common in Southern Italy (Campania, Calabria, and Sicily). We report here the hematological and hemoglobin data on 96 unrelated Sicilians with Hb lepore trait. Particularly interesting are the subjects where Hb lepore occurs with Hb S or Sicilian type delta beta-thalassemia. In these individuals, striking features are clinical variability and different hematological pictures. These observations underscore the importance of thalassemia screening in these geographic areas, such as Southern Italy, principally Sicily, where the mutations in globin gene clusters are especially prevalent. Moreover, as from the second half of the last century, owing to high migratory flux from Sicily to Northern Europe, North and South America, and Australia, the Hb lepore, as well as other hemoglobin variants, have become prevalent, making the identification of the heterozygotes a problem of general interest.