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As in most Northern European countries, the prevalence of hemoglobinopathies in The Netherlands is increasing due to migration. Although hemoglobinopathies are severe chronic diseases with few treatment options, timely detection of carriers allows at-risk couples to make informed reproductive choices such as pre-implantation diagnosis, prenatal diagnosis or termination of affected pregnancies. Using a quantitative design, we evaluated the prevalence of hemoglobinopathies in The Hague region, The Netherlands. Patient and carrier registries from hospital, laboratory and general practitioners allowed this quantitative analysis. The highest prevalence of hemoglobinopathies was seen in immigrant neighborhoods, and a large gap was noted between estimated carrier prevalence and the actual registration of carriers in electronic patient records. Carrier prevalence was estimated to be 13,704; however, the ELAN database contains only 1542 cases with ICPC codes for sickle cell disease or thalassemia. Although more research is needed to define the requirements of the healthcare system to address this challenge, this study clearly shows the gap between estimated carrier prevalence and registration and thereby the pressing need for action.

Hemoglobinopathies are the most common monogenic disorders in the world with an ever increasing global disease burden each year. As most hemoglobinopathies show recessive inheritance carriers are usually clinically silent. Programmes for preconception and antenatal carrier screening, with the option of prenatal diagnosis are considered beneficial in many endemic countries. With the development of genetic tools such as Array analysis and Next Generation Sequencing in addition to state of the art screening at the hematologic, biochemic and genetic level, have contributed to the discovery of an increasing number of rare rearrangements and novel factors influencing the disease severity over the recent years. This review summarizes the basic requirements for adequate carrier screening analysis, the importance of genotype-phenotype correlation and how this may lead to the unrevealing exceptional interactions causing a clinically more severe phenotype in otherwise asymptomatic carriers. A special group of patients are beta-thalassemia carriers presenting with features of beta-thalassemia intermedia of various clinical severity. The disease mechanisms may involve duplicated alpha-globin genes, mosaic partial Uniparental Isodisomy of chromosome 11p15.4 where the HBB gene is located or haplo-insufficiency of a non-linked gene SUPT5H on chromosome 19q, first described in two Dutch families with beta-thalassemia trait without variants in the HBB gene.

The prevalence of hemoglobinopathies in The Netherlands is increasing due to migration. Hemoglobinopathies are severe hereditary diseases. An informed reproductive choice by at-risk couples, such as pre-implantation diagnosis or termination of affected pregnancies, can be made if carriers are detected prior to conception. Using a qualitative design, the needs and wishes of patients, carriers and general practitioners were evaluated regarding carrier detection of hemoglobinopathies in primary care practice. 30 semi-structured interviews were established with 10 general practitioners, 10 patients and 10 carriers. The interviews were audio-recorded, transcribed verbatim and analysed using content analysis to identify recurring themes. Three themes were generated regarding carrier detection of hemoglobinopathies: (1) a need for more information about hemoglobinopathy, (2) a need for indications when to refer for analysis (carrier diagnostics) and (3) insight concerning organization and roles in care for hemoglobinopathy carriers and patients. These themes reflected a need to increase awareness of hemoglobinopathy, improve competences among general practitioners through better education and improvement of communication with patients and their unidentified family members. This study shows the scope of the problem and the critical need for action to improve informed reproductive decision making for the at-risk population.

Introduction The high-sequence homology of the α-globin-gene cluster is responsible for microhomology-mediated recombination events during meiosis, resulting in a high density of deletion breakpoints within a 10 kb region. Commonly used deletion detection methods, such as multiplex ligation-dependent probe amplification (MLPA) and Southern blot, cannot exactly define the breakpoints. This typically requires long-range PCR, which is not always successful. Targeted locus amplification (TLA) is a targeted enrichment method that can be used to sequence up to 70 kb of neighboring DNA sequences without prior knowledge about the target site. Methods Genomic DNA (gDNA) TLA is a technique that folds isolated DNA, ensuring that adjacent loci are in a close spatial proximity. Subsequent digestion and religation form DNA circles that are amplified using fragment-specific inverse primers, creating a library that is suitable for Illumina sequencing. Results Here, we describe the characterization of a rare 16 771 bp deletion, utilizing gDNA TLA with a single inverse PCR primer set on one end of the breakpoint. Primers for breakpoint PCR were designed to confirm the deletion breakpoints and were consequently used to characterize the same deletion in 10 additional carriers sharing comparable hematologic data and similar MLPA results. Conclusions The gDNA TLA technology was successfully used to identify deletion breakpoints within the alpha-globin cluster. The deletion was described only once in an earlier study as the --gb , but as it was not registered correctly in the available databases, it was not initially recognized as such.

Introduction The accurate measurement of HbA(2) is essential for the detection of beta-thalassaemia carriers and as no single calibrant is used by the various manufacturers of analysers, differences are seen in results obtained. The World Health Organization International Reference Reagent for HbA(2) (WHO IRR 89/666) was made available to diagnostic laboratories in the 1980s and remains the only international reference material available. A previous study (2015) demonstrated that the WHO IRR remained suitable for use as an HbA(2) standard as tested by 52 participants in the UK NEQAS Haematology Abnormal Haemoglobins Programme. This study was undertaken to include simultaneous analysis of three whole blood specimens over a range of HbA(2) values with the WHO IRR and to include participants from laboratories outside of the UK.Method Three whole blood specimens with HbA(2) levels ranging from 2.4% to 5.7% and the WHO IRR were distributed to 56 laboratories located in 14 different countries. Participants were requested to test the specimens at defined intervals and return results accompanied by chromatograms or electropherograms produced.Results Differences found in results from different analyser groups reflect the bias found in the 2015 study in that bias is seen according to the methodology used and also varies in relation to the level of analyte being measured.Conclusion Results of measurements from whole blood specimens and the lyophilized WHO IRR standard did not show any deterioration of the IRR, and it remains suitable for use. Linearity and calibration of analysers remain a problem.

Haemoglobinopathies are the commonest monogenic diseases worldwide and are caused by variants in the globin gene clusters. With over 2400 variants detected to date, their interpretation using the American College of Medical Genetics and Genomics (ACMG)/Association for Molecular Pathology (AMP) guidelines is challenging and computational evidence can provide valuable input about their functional annotation. While many in silico predictors have already been developed, their performance varies for different genes and diseases. In this study, we evaluate 31 in silico predictors using a dataset of 1627 variants in

A woman completely lacking Hb A2 on the high performance liquid chromatography (HPLC) analysis, presented with a novel deletional (eγ)δβ0-thal and a δ-globin gene variant. This combination causes a...

Accurate and consistent interpretation of sequence variants is integral to the delivery of safe and reliable diagnostic genetic services. To standardize the interpretation process, in 2015, the American College of Medical Genetics and Genomics (ACMG) and the Association for Molecular Pathology (AMP) published a joint guideline based on a set of shared standards for the classification of variants in Mendelian diseases. The generality of these standards and their subjective interpretation between laboratories has prompted efforts to reduce discordance of variant classifications, with a focus on the expert specification of the ACMG/AMP guidelines for individual genes or diseases. Herein, we describe our experience as a ClinGen Variant Curation Expert Panel to adapt the ACMG/AMP criteria for the classification of variants in three globin genes (HBB, HBA2, and HBA1) related to recessively inherited hemoglobinopathies, including five evidence categories, as use cases demonstrating the process of specification and the underlying rationale.

Methemoglobinemia is a rare disorder associated with oxidization of divalent ferro-iron of hemoglobin (Hb) to ferri-iron of methemoglobin (MetHb). Methemoglobinemia can result from either inherited or acquired processes. Acquired forms are the most common, mainly due to the exposure to substances that cause oxidation of the Hb both directly or indirectly. Inherited forms are due either to autosomal recessive variants in the CYB5R3 gene or to autosomal dominant variants in the globin genes, collectively known as HbM disease. Our recommendations are based on a systematic literature search. A series of questions regarding the key signs and symptoms, the methods for diagnosis, the clinical management in neonatal/childhood/adulthood period, and the therapeutic approach of methemoglobinemia were formulated and the relative recommendations were produced. An agreement was obtained using a Delphi-like approach and the experts panel reached a final consensus >75% of agreement for all the questions.

Objectives Artifactually altered glycated hemoglobin (HbA1c) concentrations are frequently linked to hemoglobin (Hb) variants. Their expression and detection require in-depth analysis. Methods Cation exchange high performance liquid chromatography (HPLC) (Bio-Rad Variant™ II; Trinity Biotech Premier Hb9210 Resolution), capillary electrophoresis (CE) (Sebia Capillarys 2 Flex Piercing) and mass spectrometry (MS) (Waters) were used for variant detection; Sanger sequencing, multiplex ligation-dependent probe amplification (MLPA) and next generation sequencing (NGS) were used for DNA analysis; HbA1c was measured with cation exchange HPLC (Bio-Rad Variant™ II; Arkray Adams HA-8180V; Tosoh HLC-723 G7), CE (Sebia Capillarys 2 Flex Piercing), boronate affinity HPLC (Trinity Biotech Hb9210 Premier), immunoassay (Cobas c501 Tina-quant HbA1c Gen. 3; Nihon Kohden CHM-4100 Celltac chemi HbA1c HA-411V) and enzymatic assay (Abbott Architect c 8000 HbA1c). Results Hb Yamagata [β132(H10)Lys→Asn; (HBB: c.399A>T)] was identified in the proband by MS after the observation of an abnormal peak in HPLC and CE. A mosaic expression of this variant was detected by NGS (mutant: 8%; wild type: 92%), after negative results in Sanger sequencing. Hb Yamagata interfered with HbA1c measurements by cation exchange HPLC and CE whereas immuno and enzymatic assay values showed good agreement with boronate affinity HPLC measurement. Conclusions A mosaicism of Hb Yamagata was found in a patient with altered HbA1c values. This rare gene variant was detected only by advanced technologies as MS and NGS. The variant interfered with common HbA1c determination methods.

The prevalence of hemoglobinopathies in The Netherlands is increasing due to migration. Hemoglobinopathies are severe hereditary diseases. An informed reproductive choice by at-risk couples, such as pre-implantation diagnosis or termination of affected pregnancies, can be made if carriers are detected prior to conception. Using a qualitative design, the needs and wishes of patients, carriers and general practitioners were evaluated regarding carrier detection of hemoglobinopathies in primary care practice. 30 semi-structured interviews were established with 10 general practitioners, 10 patients and 10 carriers. The interviews were audio-recorded, transcribed verbatim and analysed using content analysis to identify recurring themes. Three themes were generated regarding carrier detection of hemoglobinopathies: (1) a need for more information about hemoglobinopathy, (2) a need for indications when to refer for analysis (carrier diagnostics) and (3) insight concerning organization and roles in care for hemoglobinopathy carriers and patients. These themes reflected a need to increase awareness of hemoglobinopathy, improve competences among general practitioners through better education and improvement of communication with patients and their unidentified family members. This study shows the scope of the problem and the critical need for action to improve informed reproductive decision making for the at-risk population.

The high-sequence homology of the α-globin-gene cluster is responsible for microhomology-mediated recombination events during meiosis, resulting in a high density of deletion breakpoints within a 10 kb region. Commonly used deletion detection methods, such as multiplex ligation-dependent probe amplification (MLPA) and Southern blot, cannot exactly define the breakpoints. This typically requires long-range PCR, which is not always successful. Targeted locus amplification (TLA) is a targeted enrichment method that can be used to sequence up to 70 kb of neighboring DNA sequences without prior knowledge about the target site.Genomic DNA (gDNA) TLA is a technique that folds isolated DNA, ensuring that adjacent loci are in a close spatial proximity. Subsequent digestion and religation form DNA circles that are amplified using fragment-specific inverse primers, creating a library that is suitable for Illumina sequencing.Here, we describe the characterization of a rare 16 771 bp deletion, utilizing gDNA TLA with a single inverse PCR primer set on one end of the breakpoint. Primers for breakpoint PCR were designed to confirm the deletion breakpoints and were consequently used to characterize the same deletion in 10 additional carriers sharing comparable hematologic data and similar MLPA results.The gDNA TLA technology was successfully used to identify deletion breakpoints within the alpha-globin cluster. The deletion was described only once in an earlier study as the

Artifactually altered glycated hemoglobin (HbACation exchange high performance liquid chromatography (HPLC) (Bio-Rad Variant™ II; Trinity Biotech Premier Hb9210 Resolution), capillary electrophoresis (CE) (Sebia Capillarys 2 Flex Piercing) and mass spectrometry (MS) (Waters) were used for variant detection; Sanger sequencing, multiplex ligation-dependent probe amplification (MLPA) and next generation sequencing (NGS) were used for DNA analysis; HbAHb Yamagata [β132(H10)Lys→Asn; (A mosaicism of Hb Yamagata was found in a patient with altered HbA

Throughout the past decades, the search for a treatment for severe hemoglobinopathies has gained increased interest within the scientific community. The discovery that ɤ-globin expression from intact HBG alleles complements defective HBB alleles underlying β-thalassemia and sickle cell disease, has provided a promising opening for research directed at relieving ɤ-globin repression mechanisms and, thereby, improve clinical outcomes for patients. Various gene editing strategies aim to reverse the fetal-to-adult hemoglobin switch to up-regulate ɤ-globin expression through disabling either HBG repressor genes or repressor binding sites in the HBG promoter regions. In addition to these HBB mutation-independent strategies involving fetal hemoglobin (HbF) synthesis de-repression, the expanding genome editing toolkit is providing increased accuracy to HBB mutation-specific strategies encompassing adult hemoglobin (HbA) restoration for a personalized treatment of hemoglobinopathies. Moreover, besides genome editing, more conventional gene addition strategies continue under investigation to restore HbA expression. Together, this research makes hemoglobinopathies a fertile ground for testing various innovative genetic therapies with high translational potential. Indeed, the progressive understanding of the molecular clockwork underlying the hemoglobin switch together with the ongoing optimization of genome editing tools heightens the prospect for the development of effective and safe treatments for hemoglobinopathies. In this context, clinical genetics plays an equally crucial role by shedding light on the complexity of the disease and the role of ameliorating genetic modifiers. Here, we cover the most recent insights on the molecular mechanisms underlying hemoglobin biology and hemoglobinopathies while providing an overview of state-of-the-art gene editing platforms. Additionally, current genetic therapies under development, are equally discussed.

Background: Standardization of laboratory tests can be a long process, and this is the case with regards to the methods used to measure hemoglobin A(2) (HbA(2)), an important marker for beta-thalassemia and other thalassemic conditions. The IFCC standardization project started in 2004, and it took at least 15 years before developing a reference measurement procedure, defining and producing calibrators and certified reference materials.Methods: A series of steps have to be undertaken in order to promote the standardization in the field, a process involving a number of stakeholders (manufacturers, scientific societies, national health bodies, laboratory professionals, clinicians). In this work we describe some possible process indicators, in order to assure that the standardization will have internal and external validity and be effective for a long time. These indicators concern the inter-method studies, elaboration of External Quality Assessment Schemes, and the evaluation of the yearly distributions of HbA(2) measurements collected in selected laboratories.Results: Preliminary results are reported concerning the yearly distributions of HbA(2), collected in two different locations, and using different analytical methods. Median yearly values were found very constant over the years, but different between methods. On the other side, results obtained on the same specimens using two different techniques, proved that results by capillary electrophoresis in 2 out of the 3 years of observation, were significantly lower than those by HPLC.Conclusion: In this document we report what has been done so far, and what has to be done to achieve the standardization of the measurement of HbA(2) worldwide.

We describe a first Dutch case of Hb M Saskatoon (HBB:c.190C > T p.His64Tyr) in a 47-year-old female Dutch patient who presented with cyanosis, hemolysis, and abnormal co-oximetry. A mean corpuscular volume (MCV) of 105 fL caused by reticulocytosis (160 x 10(9)/L) and low red blood cell count (3.6 x 10(12)/L) suggested an increased erythrocyte turnover. An HPLC glyco-globin analysis revealed a decreased HbA1c fraction of 12.3 mmol/mmol, HbA0 of 93.3% and an additional unidentified fraction at 1.2 min. DNA sequencing revealed a missense mutation in the HBB gene, (HBB:c.190C > T p.His64Tyr), known as Hb M Saskatoon, a variant which has been previously identified as an unstable hemoglobin variant leading to methemoglobinemia and anemia. In this report, we describe the clinical and remarkable laboratory aspects of our patient with Hb M Saskatoon, and the consequences for treatment and drug use.

Standardization of laboratory tests can be a long process, and this is the case with regards to the methods used to measure hemoglobin AA series of steps have to be undertaken in order to promote the standardization in the field, a process involving a number of stakeholders (manufacturers, scientific societies, national health bodies, laboratory professionals, clinicians). In this work we describe some possible process indicators, in order to assure that the standardization will have internal and external validity and be effective for a long time. These indicators concern the inter-method studies, elaboration of External Quality Assessment Schemes, and the evaluation of the yearly distributions of HbAPreliminary results are reported concerning the yearly distributions of HbAIn this document we report what has been done so far, and what has to be done to achieve the standardization of the measurement of HbA

We report a newborn with a compound heterozygosity for Hb O-Arab (

We report a newborn with a compound heterozygosity for Hb O-Arab (HBB: 364G>A) and Hb D-Los Angeles (HBB: 364G>C). To the best of our knowledge, the combination of these two hemoglobin (Hb) variants has not been identified and reported before. The variants of the proband and parents were identified by high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE). DNA analysis was performed to confirm the variants. The levels of Hb variants of the proband were determined post-partum, at 3 months and 1 year after birth. Blood count analysis after 1 year revealed that the proband had a mild microcytic anemia. Furthermore, HPLC and CE analysis revealed an equal distribution of Hb D-Los Angeles compared to Hb O-Arab at the age of 1 year. The follow-up of the patient, suggested that the Hb combination is clinically silent or mild.

BackgroundSporadic deletions removing 100s-1000s kb of DNA, and variable numbers of poorly characterised genes, are often found in patients with a wide range of developmental abnormalities. In such cases, understanding the contribution of the deletion to an individual’s clinical phenotype is challenging.MethodsHere, as an example of this common phenomenon, we analysed 34 patients with simple deletions of ∼177 to ∼2000 kb affecting one allele of the well characterised, gene dense, distal region of chromosome 16 (16p13.3), referred to as ATR-16 syndrome. We characterised precise deletion extent and screened for genetic background effects, telomere position effect and compensatory up regulation of hemizygous genes.ResultsWe find the risk of developmental and neurological abnormalities arises from much smaller terminal chromosome 16 deletions (∼400 kb) than previously reported. Beyond this, the severity of ATR-16 syndrome increases with deletion size, but there is no evidence that critical regions determine the developmental abnormalities associated with this disorder. Surprisingly, we find no evidence of telomere position effect or compensatory upregulation of hemizygous genes, however, genetic background effects substantially modify phenotypic abnormalities.ConclusionsUsing ATR-16 as a general model of disorders caused by sporadic copy number variations, we show the degree to which individuals with contiguous gene syndromes are affected is not simply related to the number of genes deleted but also depends on their genetic background. We also show there is no critical region defining the degree of phenotypic abnormalities in ATR-16 syndrome and this has important implications for genetic counselling.

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Introduction The accurate determination of Hb A2 is a key marker when screening for a β-thalassaemia carrier. Data from external quality assessment (EQA) exercises have shown a lack of alignment of Hb A2 quantitation both within and between methods. The only reference material available for Hb A2 quantitative assay at the time of writing is the World Health Organization International Reference Reagent (89/666; WHO IRR) prepared in the 1980s and not validated for all current methodologies. Method The WHO IRR was analysed for Hb A2 concentration by 52 laboratories using a representative range of high-performance liquid chromatography and capillary electrophoresis analysers. The results of the analysis were compared to those of a whole blood EQA specimen of similar Hb A2 concentration, distributed in the same week. Results The mean Hb A2 value obtained for the WHO IRR was 5.17%, compared to the assigned value of 5.3%. The range of results returned was wide (4.0%-6.2%), with differences in the results observed by between and within analyser groups. A similar range of results was seen with the whole blood sample, although the bias observed between analyser types was different from that seen with the WHO IRR. Conclusion The results may indicate a lack of commutability of the WHO IRR material, resulting from deterioration, matrix effects or changes in reagent formulation or calibration parameters. Further examination of the suitability of the WHO IRR (89/666) for continued use is required.

We report two families, members of which are carriers of a hemoglobin (Hb) variant previously described as Hb Nouakchott [α114(GH2)Pro→Leu; HBA1: c.344C>T; p.Pro115Leu]. In the first family of Dutch origin, the proband, a 32-year-old male and his 65-year-old father, were both carriers of Hb Nouakchott. Of the second family we tested, only the proband, a 56-year-old Dutch female was a Hb Nouakchott carrier. Hematological analyses of these cases showed the anomaly behaves as a silent Hb variant without clinical consequences. The Hb variant remained unnoticed using high performance liquid chromatography (HPLC), while an additional peak was detected by capillary electrophoresis (CE). These independent findings of Hb Nouakchott indicate that this Hb variant might not be very rare, but simply remains under diagnosed depending on the Hb separation technique used

Sequence variants located in the introns of the β-globin gene may affect the mRNA processing and cause β-thalassemia (β-thal). Sequence variants that change one of the invariant dinucleotides at the exon-intron boundaries may have fatal consequences for normal mRNA splicing. Intronic variants located far from obvious regulatory sequences can be more difficult to evaluate. There is a potential for misinterpretation of such sequence variants. Hence, thorough evaluation of patient data together with critical use of databases and in silico prediction tools are important. Here, we describe two rare sequence variants in the second intron of the β-globin gene, HBB: c.316-70C>G and HBB: c.316-125A>G (NM_000518.4), both previously reported as variants causing β-thal, and later as benign sequence variants. Due to the limited number of published cases and inconsistent interpretations, the significance of these sequence variants has been unclear. We have identified these two sequence variants in multiple individuals, alone and in a variety of combinations with other δ- and β-globin defects, and we find no influence of the sequence variants on the phenotype.

The accurate determination of Hb AThe WHO IRR was analysed for Hb AThe mean Hb AThe results may indicate a lack of commutability of the WHO IRR material, resulting from deterioration, matrix effects or changes in reagent formulation or calibration parameters. Further examination of the suitability of the WHO IRR (89/666) for continued use is required.

Background Most of the current methods used for the determination of HbA2 seem not well aligned. A comparison among the best performing techniques and the commutability of some control materials currently available and under development has been evaluated. Methods Forty blood samples were analyzed in duplicate over two separate days by different HPLC and capillary electrophoresis systems. The commutabilities of different control materials (NIBSC WHO reagent, Bio-Rad Lyphochek, and home prepared lyophilized controls RP1–3) have been assessed by analyzing the controls in quadruplicate over two consecutive days together with the blood samples. Results The mean within-run imprecision of HbA2 measurement on blood samples (CV, %) was between 0.6% and 10.1% for HbA2 values Conclusion The use of adequate commutable control materials as calibrators may reduce the inter-method variability of routine methods to an extent closer to the current analytical goals of bias based on biological variability.

Hemoglobinopathies constitute the most common severe monogenic disorders worldwide, with an increasing global burden each year. The benefit of applying programmes for preconception carrier screening, with the option of prenatal diagnosis, to minimize the incidence of new cases is recognized in many countries. Areas covered: The challenges associated with identifying carrier couples using hematology-based screening, along with DNA diagnosis and prenatal diagnosis were addressed, based on a literature search and the authors expertise. Expert commentary: The hemoglobinopathies are extremely heterogeneous at the haematological, molecular and clinical level, requiring appropriately equipped and staffed laboratories with experience to support comprehensive screening and diagnosis. However complete services with adequate infrastructure to address the associated technical challenges do not exist widely, especially in low-income countries that, coincidentally, are often those with the highest frequency of hemoglobinopathies in their population. Additionally, overcoming limited public awareness, education and absence of systematic dissemination of information also constitutes a challenge. This article aims to highlight these challenges and to evaluate potential future developments that may address at least some of them, focusing mainly on the technical challenges related to molecular diagnostics.

Most of the current methods used for the determination of HbAForty blood samples were analyzed in duplicate over two separate days by different HPLC and capillary electrophoresis systems. The commutabilities of different control materials (NIBSC WHO reagent, Bio-Rad Lyphochek, and home prepared lyophilized controls RP1-3) have been assessed by analyzing the controls in quadruplicate over two consecutive days together with the blood samples.The mean within-run imprecision of HbAThe use of adequate commutable control materials as calibrators may reduce the inter-method variability of routine methods to an extent closer to the current analytical goals of bias based on biological variability.

We report two examples showing how problematic it can be to define the phenotype of new or rare globin genes mutations. We describe two mutations observed for the first time in the Omani population: the first was found in the consanguineous parents of a deceased newborn with hepatomegaly, cardiomegaly and severe hemolytic anemia, putatively homozygous for the rare Hb Lansing (HBA2: c.264C > G) variant. The second is a novel β-globin gene promoter mutation [−52 (G > T)] observed in four independent patients. Two with borderline/elevated Hb A2, α-thalassemia (α-thal) and hypochromic red cell indices, and two heterozygotes for Hb S (HBB: c.20A > T), α-thal and with Hb A/Hb S ratios possibly indicating a very mild β+-thalassemia (β+-thal) mutation.

The objective of this study was to expand and study the molecular spectrum of β-thalassemia (β-thal) mutations in Oman by examining cases from seven different regions and comparing the prevalence with neighboring countries. A total of 446 cases of β hemoglobinopathies was obtained and analyzed to determine the frequency and distribution of the different β alleles. The molecular spectrum of β-thal in Oman revealed the presence of 32 mutations from different origins and 11 alleles are reported for the first time in the Omani population. The wide heterogeneous spectrum of β-thal mutations found can be associated with the history of trade and migration as well as the past domination from other countries. The presented data will facilitate the development of a comprehensive prevention strategy in Oman.

We describe the molecular characterization of α-globin gene defects in a cohort of 634 Omani patients. A total of 21 different α gene mutations were found in 484 subjects. Overall, we identified three different large deletions, three small deletions, 11 point mutations [two on the α2 polyadenylation signal (polyA) (HBA2: c.*94A>G), and nine α chain variants], three αααanti 3.7 triplication, a 21 nucleotide (nt) duplication on the α1 gene and two novel (presumed) polymorphisms on the α 3.7 kb hybrid gene, namely −5 (C>T) and +46 (C>A). Of these defects, 15 have not been previously reported in the Omani population. This large heterogeneity of α-thalassemia (α-thal) observed in the Omani population could be expected in neighboring Arab countries. The high frequency of α-thal, solely or in association with β-globin gene defects, emphasize the necessity of adding α-thal testing to pre marital programs for accurate genetic counseling.

α-Thalassemia is an inherited, autosomal recessive, disorder characterized by a microcytic hypochromic anemia. It is one of the most common monogenic gene disorders in the world population. The clinical severity varies from almost asymptomatic, to mild microcytic hypochromic, and to a lethal hemolytic condition, called Hb Bart's Hydrops Foetalis Syndrome. The molecular basis are usually deletions and less frequently, point mutations affecting the expression of one or more of the duplicated α-genes. The clinical variation and increase in disease severity is directly related to the decreased expression of one, two, three or four copies of the α-globin genes. Deletions and point mutations in the α-globin genes and their regulatory elements have been studied extensively in carriers and patients and these studies have given insight into the α-globin genes are regulated. By looking at naturally occurring deletions and point mutations, our knowledge of globin-gene regulation and expression will continue to increase and will lead to new targets of therapy.