Incidence of haemoglobinopathies in various populations — The impact of immigration

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.

Characterization and Clinical Assessment of a Peculiar Case of Hemolytic Anemia

Thalassemic diseases are characterized by a reduced (β+) or absent (β0) synthesis of the globin chains of hemoglobin (Hb) due to genetic mutations. β-thalassemia was more frequent in the Mediterranean area, but now it is diffused worldwide. Three possible genetic forms can be distinguished: β0/β0, the most severe (Cooley's disease); β0/β+ of intermediate severity; β+/β+ associated with β-thalassemia intermedia or minor. Recently, a clinical non-genetic classification has been proposed: transfusion-dependent thalassemia (TDT), requiring regular lifetime blood transfusions, and non-transfusion-dependent thalassemia (NTDT), requiring occasional transfusions to manage acute cases. In this report, we studied a patient whose blood count indicated a severe anemia but also showed thrombocytosis, leukocytosis, and an elevated number of nucleated red blood cells (NRBC). These altered blood parameters suggested initially a possible diagnosis of hemoglobinopathy or myeloproliferative syndrome. The molecular and genetic analyses demonstrated the presence of HbF (5.3%) and HbA2 (7.7%) and the presence of the homozygote mutation (IVS1.6T>C) in the β-globin gene. According to these data, a diagnosis of β-thalassemia intermedia form has been proposed. Nevertheless, the clinical condition, the presence of thrombocytosis, leukocytosis, an elevated number of NRBC, and the frequent blood transfusions lead to reclassification of the patient as TDT subject. Consequently, this result suggests that a unique genotype-phenotype correlation is not possible in the presence of β+mutations since other concomitant pathologies can exacerbate the disease.

Hemoglobin β-Globin Variants In Hispanic Patients: An Institutional Experience From Dallas, Texas

Hemoglobinopathies are the most common single-gene disorders in humans. There are 1,424 variants of human hemoglobin described with 951 involving the β-globin gene. Ancestry and geography play a significant role in the incidence and nature of hemoglobinopathies, with African, Asian, and Mediterranean populations and their descendants being amongst the most affected. Investigation of variants in individuals of Hispanic descent is needed to reflect the changing demographics of the United States. Hemoglobin β-globin evaluation through gel electrophoresis, high-performance liquid chromatography, and HBB gene sequencing was performed on patients from Texas hospitals between 2010 and 2015 and demographic parameters (age, sex, ethnicity) was subsequently analyzed. A total of 846 patients underwent hemoglobinopathy evaluation. A β chain variant was detected in 628 of the 846 total patients. Hispanic patients represented 37% (314/846 patients), which were equally distributed between females (50%; 156/314) and males (50%; 156/314). A β-globin chain variant was found in 67% of Hispanic patients with a distribution across 10 variants seen in greater than 1% of patients. For hemoglobin variants, an understanding of the regional and ethnic prevalence will improve patient care through more effective screening and identification of the variant, early diagnosis, and appropriate treatment if necessary, and better genetic counseling.

Celocentesis for Early Prenatal Diagnosis in Couples at-Risk for β-Thalassemia and Sicilian (δβ)0-Thalassemia

The procedures commonly used for prenatal diagnosis (PND) of thalassemia are villocentesis or amniocentesis, respectively, at the 11th and 16th weeks of gestation. Their main limitation is essentially due to the late gestation week in which diagnosis is performed. The celomic cavity is accessible between the 7th and 9th weeks of gestation and it has been demonstrated that it contains embryonic erythroid precursor cells as a source of fetal DNA for earlier invasive PND of thalassemia and other monogenic diseases. In this study, we report the use of celomatic fluids obtained from nine women with high-risk pregnancies for Sicilian (δβ)⁰-thalassemia [(δβ)⁰-thal] deletion (NG_000007.3: g.64336_77738del13403) and β-thalassemia (β-thal). Fetal cells were isolated by a micromanipulator, and nested polymerase chain reaction (PCR) and short tandem repeats (STRs) analysis were performed. Prenatal diagnosis was successfully performed in all examined cases. One fetus was a compound heterozygote for (δβ)⁰- and β-thal, three fetuses were found to be carriers of β-thal, four fetuses carriers of a Sicilian δβ deletion, and one fetus without parental mutations. Accidentally, a rare case of paternal triploidy was observed. The genotypic analysis, carried out both by amniocentesis and on abortive tissue or after birth, showed concordance with results obtained on fetal celomic DNA. Our results unequivocally show that fetal DNA can be obtained by nucleated fetal cells present in the celomatic fluid and demonstrate, for the first time, that PND of Sicilian (δβ)⁰-thal and β-thal is feasible at an earlier time in pregnancy than other procedures.

The spectrum of beta-thalassemia mutations in the 22 Arab countries: a systematic review

OBJECTIVES

To investigate the mutational spectrum in the HBB gene in Arab patients with β-thal.

METHODS

Authors searched five databases (PubMed, Science Direct, Scopus, Web of Science, and Google Scholar) from the time of inception until March 2020.

RESULTS

The authors search strategy yielded 3,229 citations, of which 48 eligible studies captured. 105 mutations were captured, of these, 99 were shared between Arabs and other ethnic groups, six mutations were unique to Arabs (c.92 + 2 T > G, c.-240 G > A, c.150delC, c.420dupT, deletion of 192 bp spanning exon 1, intron 1, and the first two bases of exon 2 of HBB gene, and deletion of 9.6 kb, including exon 1 and intron 2 of HBB gene). The most common HBB gene mutations among Arabs were c.93-21 G > A, c.118 C > T, c.92 + 1 G > A, c.92 + 6 T > C, c.92 + 5 G > C, c.315 + 1 G > A, and c.27dupG. Consanguinity is high among Arab patients with β-thal. Migration into Arab countries led to allelic heterogeneity among Arab patients with β-thal.

CONCLUSION

Our findings present a platform for further genetic epidemiological studies for Arab patients with β-thal.

Genetic Modifiers at the Crossroads of Personalised Medicine for Haemoglobinopathies

Haemoglobinopathies are common monogenic disorders with diverse clinical manifestations, partly attributed to the influence of modifier genes. Recent years have seen enormous growth in the amount of genetic data, instigating the need for ranking methods to identify candidate genes with strong modifying effects. Here, we present the first evidence-based gene ranking metric (IthaScore) for haemoglobinopathy-specific phenotypes by utilising curated data in the IthaGenes database. IthaScore successfully reflects current knowledge for well-established disease modifiers, while it can be dynamically updated with emerging evidence. Protein-protein interaction (PPI) network analysis and functional enrichment analysis were employed to identify new potential disease modifiers and to evaluate the biological profiles of selected phenotypes. The most relevant gene ontology (GO) and pathway gene annotations for (a) haemoglobin (Hb) F levels/Hb F response to hydroxyurea included urea cycle, arginine metabolism and vascular endothelial growth factor receptor (VEGFR) signalling, (b) response to iron chelators included xenobiotic metabolism and glucuronidation, and (c) stroke included cytokine signalling and inflammatory reactions. Our findings demonstrate the capacity of IthaGenes, together with dynamic gene ranking, to expand knowledge on the genetic and molecular basis of phenotypic variation in haemoglobinopathies and to identify additional candidate genes to potentially inform and improve diagnosis, prognosis and therapeutic management.

New Challenges in Diagnosis of Haemoglobinopathies: Migration of Populations

The current influx of economic migrants and asylum seekers from countries with a high prevalence of haemoglobinopathies creates new challenges for health care systems and diagnostic laboratories. The migration of carriers introduces new and novel haemoglobinopathy mutations to the diagnostic repertoire of a laboratory, often creating new pressures to improve and update the carrier screening technology and diagnostic scope. For antenatal screening programmes, the marriage of partners from different ethnic groups can lead to the risk of compound heterozygote children being born novel mutation combinations, creating problems in the provision of accurate advice regarding the expected phenotype of the thalassaemia or haemoglobinopathy disorder. In the UK, the impact of immigration required the National Haemoglobinopathy Reference laboratory to change the strategy and techniques used for the molecular diagnosis of thalassaemia and the haemoglobinopathies. In 2005, due to the increasingly large range of β-thalassaemia mutations that needed to be diagnosed, the laboratory switched from a three-step screening procedure using ARMS-PCR to a simpler but more expensive one-step strategy of DNA sequencing of the beta and alpha globin genes for all referrals. After ten years of employing this strategy, a further 57 novel thalassaemia and haemoglobionpopthy alleles were discovered (11 new β-chain variants, 15 α-chain variants, 19 β-thalassaemia mutations and 12 α+-thalassaemia mutations), increasing further the extremely heterogeneous spectrum of globin gene mutations in the UK population.

Racial variation in cardiovascular disease risk factors among European children on renal replacement therapy-results from the European Society for Paediatric Nephrology/European Renal Association - European Dialysis and Transplant Association Registry

Background

Racial differences in overall mortality rates have been found in children on renal replacement therapy (RRT). We used data from the European Society for Paediatric Nephrology/European Renal Association - European Dialysis and Transplant Association Registry to study racial variation in the prevalence of cardiovascular disease (CVD) risk factors among European children on RRT.

Methods

We included patients aged <20 years between 2006-13 who (i) initiated dialysis treatment or (ii) had a renal transplant vintage of ≥1 year. Racial groups were defined as white, black, Asian and other. The CVD risk factors assessed included uncontrolled hypertension, obesity, hyperphosphataemia and anaemia. Differences between racial groups in CVD risk factors were examined using generalized estimating equation (GEE) models while adjusting for potential confounders.

Results

In this study, 1161 patients on dialysis and 1663 patients with a transplant were included. The majority of patients in both groups were white (73.8% and 79.9%, respectively). The crude prevalence of the CVD risk factors was similar across racial groups. However, after adjustment for potential confounders, Asian background was associated with higher risk of uncontrolled hypertension both in the dialysis group [odds ratio (OR): 1.27; 95% confidence interval (CI): 1.01-1.64] and the transplant group (OR: 1.37; 95% CI: 1.11-1.68) compared with white patients. Patients of Asian and other racial background with a renal transplant had a higher risk of anaemia compared with white patients (OR: 1.50; 95% CI: 1.15-1.96 and OR: 1.45; 95% CI: 1.01-2.07, respectively). Finally, the mean number of CVD risk factors among dialysis patients was higher in Asian patients (1.83, 95% CI: 1.64-2.04) compared with white patients (1.52, 95% CI: 1.40-1.65).

Conclusions

We found a higher prevalence of modifiable CVD risk factors in Asian children on RRT. Early identification and management of these risk factors could potentially improve long-term outcomes.

Ten Years of Routine α- and β-Globin Gene Sequencing in UK Hemoglobinopathy Referrals Reveals 60 Novel Mutations

We review and report here the genotypes and phenotypes of 60 novel thalassemia and abnormal hemoglobin (Hb) mutations discovered following the adoption of routine DNA sequencing of both α- and β-globin genes for all UK hemoglobinopathy samples referred for molecular investigation. This screening strategy over the last 10 years has revealed a total of 11 new β chain variants, 15 α chain variants, 19 β-thalassemia (β-thal) mutations and 15 α(+)-thalassemia (α(+)-thal) mutations. The large number of new thalassemia alleles confirms the wide racial heterogeneity of mutations in the UK immigrant population. Eleven of the new variants ran with Hb A on high performance liquid chromatography (HPLC), demonstrating the value of routine sequencing of both α- and β-globin genes for all hemoglobinopathy investigations. The new β chain variants are: Hb Bury [β22(B4)Glu  →  Asp (HBB: c.69A > T)], Hb Fulwood [β35(C1)Tyr → His (HBB: c.106T > C)], Hb Little Venice [β42(CD1)Phe → Cys (HBB: c.128T > G)], Hb Cork [β57(E1)Asn → Ser (HBB: c.173A > G), Hb Basingstoke [β118(GH1)Phe → Ser (HBB: c.356T > C)], Hb Howden [β20(B2)Val → Ala (HBB: c.62T > C)], Hb Wilton [β41(C7)Phe → Leu (HBB: c.126C > A)], Hb Belsize Park [β120(GH3)Lys → Asn (HBB: c.363A > T)], Hb Hampstead Heath [β2(NA2)His → Gln;β26(B8)Glu → Lys (HBB: c.[6C > G;79G > A])], Hb Grantham [β85(F1)Phe → Cys (HBB: c.257T > G)] and Hb Calgary [β64(E8)Gly → Val (HBB: c.194G > T). The new α chain variants are: Hb Edinburgh [α70(E19)Val → Gly (HBA2: c.212T > G)], Hb Walsgrave [α116(GH4)Glu → Val (HBA2: c.350A > T)], Hb Wexham [α117(GH5) and 118(H1) insertion Ser (HBA1: c.354-355insTCA)], Hb Coombe Park [α127(H10)Lys → Glu (HBA2: c.382A > G)], Hb Oxford [α17(A15)Val → Asp (HBA2: c.53T > A)], Hb Bridlington [α32(B13)Met → Thr (HBA1: c.98T > C), Hb Wolverhampton [α81(F2)Ser → Tyr (HBA2: c.9245C > A)], Hb Little Waltham [α13(A11)Ala → Asp (HBA2: c.41C > A)], Hb Derby [α61(E10)Lys → Arg (HBA1: c.185A > G)], Hb Uttoxter [α74(EF3)Tyr → Asp (HBA2: c.223G > T)], Hb Harehills [α124(H7)Ser → Cys (HBA1: c.374C > G)], Hb Hekinan II [α27(B8)Glu → Asp (HBA1: c.84G > T)], Hb Manitoba IV [α102(G9)Ser → Arg (HBA1: c.307A > C), Hb Witham [α139(HC1)Lys → Arg (HBA2: c.419A > G) and Hb Farnborough [α9(A7)Asn → Asp (HBA1: c.28A > G). In addition, 10 more paralogous α-globin chain variants have been discovered. The novel β-thal alleles are: HBB: c.-138C > G, HBB: c.-121C > T, HBB: c.-80T > G, HBB: c.18_19delTG, HBB: c.219_220insT, HBB: c.315 + 2_315 + 13delTGAGTCTATGGG, HBB: c.316-70C > G, HBB: c.345_346insTGTGCTG, HBB: c.354delC, HBB: c.376-381delCCAGTG, HBB: c.393T > A, HBB: c.394_395insA, HBB: c.375_376insA, HBB: c.*+95_*+107delTGGATTCTinsC, HBB: c.* + 111_*+112delAA, HBB: c.*+112A > T, HBB: c.394C > T, HBB: c.271delG and HBB: c.316-3C > T. The novel α (+ )-thal alleles are: HBA1: c.95+1G > C, HBA1: c.315C > G [Hb Donnington, α104(G11)Cys → Trp], HBA1: c.327delC, HBA1: c.333_345del, HBA1: c.*+96G > A, HBA2: c.2T > G, HBA2: c.112delC, HBA2: c.143delA, HBA2: c.143_146delACCT, HBA2: c.156_157insG, HBA2: c.220_223delGTGG, HBA2: c.305T > C [Hb Bishopstown, α101(G8)Leu → His], HBA2: c.169_170delAA, HBA2: c.1A > T and HBA2: c.-3delA.

Thalassemia and sickle cell anemia in Swedish immigrants: Genetic diseases have become global

Aims:

Some 15% of the Swedish population is born outside Sweden, originating from all continents of the world. Thalassemia and sickle cell anemia constitute the most common inherited recessive disorders globally and they are endemic in areas of Africa and Asia, origins of many immigrants to Sweden. We aimed at investigating the origins of the Swedish sickle cell and thalassemia patients.

Methods:

Patients were identified using data from the Swedish Hospital Discharge Register since 1987 and from the Outpatient Register since 2001 up to year 2010.

Results:

A total of 3064 persons were diagnosed with thalassemia. The incidence was highest, 62.9/100,000 for immigrants from Thailand, followed by Iraqis (47.1/100,000); the rate was 0.7/100,000 among those born in Sweden. The total number of sickle cell anemia patients was 584 and the highest rate of 13.0/100,000 was found for Sub-Saharan immigrants. For thalassemia, 363 of the patients were siblings, while for sickle cell anemia, 180 were siblings.

Conclusions:

The data showed that >90% of sickle cell and thalassemia patients were first- or second-generation immigrants to Sweden and the endemic regions for these were the origins of immigrants with the highest incidence. Global immigration provides global challenges to national health care systems.

Antenatal haemoglobinopathy screening: Patterns within a large obstetric service. Working towards a standard of care

BACKGROUND

Antenatal screening can predict clinically significant haemoglobinopathies, however in Australia, practices are not standardised and are evolving as the population becomes more ethnically diverse. This study describes antenatal screening practices in a large Australian laboratory/antenatal service.

METHODS

Data were collected retrospectively on consecutive antenatal haemoglobin electrophoresis over 16 months and correlated with obstetric data, obtained from the local obstetric database.

RESULTS

462 patients were included, with an average gestation of 25.8 weeks. 'Pregnancy' was the most common stated indication, with absent indication/clinical information in 8%. Gestational age was documented in 54%. In 15%, no contact details of the referrer were documented and partner screening was traceable in only 25 cases (5.4%). In 82% of cases, no abnormalities were detected. Beta thalassemia trait was the most common positive result. Only 52% of patients had recent iron studies. The mean haemoglobin was 111.6 g/L and mean cell volume was 80.5 fl at the time of testing. Ethnicity was documented on the request form in 3%. After Australasia, the most common ethnicity of patients was South East Asia and the Middle East.

CONCLUSION

Referral patterns in our health service are diverse and reflect our changing population and care practices. Detailed guidelines are required and we propose a comprehensive algorithm for general use where selective screening is practiced within an Australasian population or one with similar demographics.

Gap-PCR Screening for Common Large Deletional Mutations of β-Globin Gene Cluster Revealed a Higher Prevalence of the Turkish Inversion/Deletion (δβ)0 Mutation in Antalya

OBJECTIVE

Although the calculated carrier frequency for point mutations of the β-globin gene is around 10% for Antalya Province, nothing is known about the profile of large deletional mutations involving the β-globin gene. In this study, we aimed to screen common deletional mutations in the β-globin gene cluster in patients for whom direct DNA sequencing was not able to demonstrate the mutation(s) responsible for the disease phenotype.

MATERIALS AND METHODS

Thirty-one index cases selected with a series of selection events among 60 cases without detected β-globin gene mutation from 580 thalassemia-related cases tested by direct sequencing over the last 4 years in our diagnostic center were screened for the most common 8 different large deletional mutations of the β-globin gene cluster by gap-PCR.

RESULTS

We detected 1 homozygous and 9 heterozygous novel unrelated cases for the Turkish inversion/deletion (δβ)0 mutation in our series of 31 cases. Our study showed that the Turkish inversion/deletion (δβ)0 mutation per se accounts for 16.6% of the unidentified causative alleles and also accounts for 1.5% of all detected mutations over the last 4 years in our laboratory.

CONCLUSION

Since molecular diagnosis of deletional mutations in the β-globin gene cluster warrants different approaches, it deserves special attention in order to provide prenatal diagnosis and prevention opportunities to the families involved. We conclude that the Turkish inversion/deletion (δβ)0, as the most prevalent deletional mutation detected so far, has to be routinely tested for in Antalya, and the gap-PCR approach has valuable diagnostic potential in the patients at risk.

Prevalence of hemoglobinopathies in school children: the importance of using confirmatory methods

<p>The hemoglobinopathies are included among the most common genetic diseases in the world. In Brazil, hemoglobinopathies are related to the diversity of racial backgrounds and the degree of interbreeding. The study focused on the prevalence of hemoglobinopathies using conventional and confirmatory laboratory tests in children from public schools in Ribeirão Preto-SP. The study involved the participation of 427 children between six and nine years of age. Hematologic evaluation, hemoglobin electrophoresis on cellulose acetate at alkaline pH, quantification of hemoglobin fractions by high performance liquid chromatography (HPLC) and detection of -α^3.7 deletion for α thalassemia by polymerase chain reaction were performed. The results of hemoglobin electrophoresis on cellulose acetate and HPLC of the children studied showed the presence of 30 children (7%) with hemoglobinopathies. Eleven children presented results indicating suspicion of S/β-thalassemia; their parents and/or siblings were evaluated and confirmed the presence of only Hb S. The analysis of deletion -α^3.7to characterize α-thalassemias sampling performed on 207 participants identified 26 children (12.6%) with deletion -α^3.7. Thus, 54 (12.6%) of the children studied present this genetic alteration. For the detection of α-thalassemias it is necessary to use confirmatory methods such as molecular analysis and evaluation of family members in doubtful cases to facilitate genetic counseling in families, in which deletion -α^3.7 is more frequent in Brazil.</p>

Consanguinity and genetic diseases in North Africa and immigrants to Europe

Endemic diseases are caused by environmental and genetic factors. While in this special issue several chapters deal with environmental factors, including infections, the present focus is on genetic causes of disease clustering due to inbreeding and recessive disease mechanisms. Consanguinity is implying sharing of genetic heritage because of marriage between close relatives originating from a common ancestor. With limited natural selection, recessive genes may become more frequent in an inbred compared with an outbred population. Consanguinity is common in North Africa (NA), and the estimates range from 40 to 49% of all marriages in Tunisia and 29-33% in Morocco. As a consequence, recessive disorders are common in the NA region, and we give some examples. Thalassaemia and sickle cell disease/anaemia constitute the most common inherited recessive disorders globally and they are common in NA, but with immigration they have spread to Europe and to other parts of the world. Another example is familial Mediterranean fever, which is common in the Eastern Mediterranean area. With immigrantion from that area to Sweden, it has become the most common hereditary autoinflammatory disease in that country, and there is no evidence that any native Swede would have been diagnosed with this disease. The examples discussed in this chapter show that the historic movement of populations and current immigration are influencing the concept of 'endemic' disease.

IthaGenes: an interactive database for haemoglobin variations and epidemiology

Inherited haemoglobinopathies are the most common monogenic diseases, with millions of carriers and patients worldwide. At present, we know several hundred disease-causing mutations on the globin gene clusters, in addition to numerous clinically important trans-acting disease modifiers encoded elsewhere and a multitude of polymorphisms with relevance for advanced diagnostic approaches. Moreover, new disease-linked variations are discovered every year that are not included in traditional and often functionally limited locus-specific databases. This paper presents IthaGenes, a new interactive database of haemoglobin variations, which stores information about genes and variations affecting haemoglobin disorders. In addition, IthaGenes organises phenotype, relevant publications and external links, while embedding the NCBI Sequence Viewer for graphical representation of each variation. Finally, IthaGenes is integrated with the companion tool IthaMaps for the display of corresponding epidemiological data on distribution maps. IthaGenes is incorporated in the ITHANET community portal and is free and publicly available at http://www.ithanet.eu/db/ithagenes.

Advances in technologies for screening and diagnosis of hemoglobinopathies

Hemoglobinopathies constitute the most common monogenic disorders worldwide, caused by mutations in the globin genes that synthesize the globin chains of hemoglobin. Synthesis may be reduced (thalassemia) or underlie abnormal hemoglobins. Mutation interactions produce a wide range of disorders. For neonatal and antenatal screening, identification of affected newborns or carriers is achieved by hematological tests. DNA analysis supports definitive diagnosis, and additionally facilitates prenatal diagnosis procedures. Most methods used today have been developed over several decades, with few recent advances in hematology methods. However, DNA methods evolve continuously. With global migration and multiethnic societies the trend is from targeted, population-specific methods towards generic methods, such as Sanger sequencing (point mutations) and multiplex ligation probe amplification (deletions). DNA microarrays constitute an advanced DNA method for some mutation categories. The newest DNA technology is next-generation sequencing. Although not completely ready for routine use currently, next-generation sequencing may soon become a reality for some hemoglobin diagnostic laboratories.

Molecular Diagnostics of β-Thalassemia

A high-quality hemoglobinopathy diagnosis is based on the results of a number of tests including assays for molecular identification of causative mutations. We describe the current diagnostic strategy for the identification of β-thalassemias and hemoglobin (Hb) variants at the International Reference Laboratory for Haemoglobinopathies, Research Centre for Genetic Engineering and Biotechnology (RCGEB) “Georgi D. Efremov,” Skopje, Republic of Macedonia. Our overall approach and most of the methods we use for detection of mutations are designed for the specific target population. We discuss new technical improvements that have allowed us to substantially reduce the average time necessary for reaching a conclusive diagnosis.

Epidemiological profile of common haemoglobinopathies in Arab countries

Haemoglobinopathies including the thalassemias and sickle cell disease are known to be prevalent inherited disorders in most Arab countries with varying prevalence rates and molecular characterisation. β-thalassemia is encountered in polymorphic frequencies in almost all Arab countries with carrier rates of 1-11 % and a varying number of mutations. The most widespread mutation in Lebanon, Egypt, Syria, Jordan, Tunisia and Algeria is the IVS-I-110 (G>A). In the Eastern Arabian Peninsula, the Asian Indian mutations (IVS-I-5 (G>C), codons 8/9 (+G) and IVS-I (-25 bp del)) are more common. The α-thalassemias are encountered in the majority of Arab countries in frequencies ranging from 1 to 58 % with the highest frequencies reported from Gulf countries. The (-α(3.7)) mutation is the most frequent followed by the non-deletional α2 polyadenylation signal mutation (AATAAA>AATAAG) and the α2 IVS1 5-bp deletion. The rates of sickle cell trait in Arab countries range from 0.3 to 30 %, with the Benin, the Arab-Indian and the Bantu haplotypes constituting the bulk of the haplotypes, leading to two major phenotypes; a mild one associated with the Arab-Indian and a severe one with the Benin and Bantu haplotypes. Public health approaches targeting prevention of haemoglobinopathies in Arab countries include newborn screening for sickle cell disease, and premarital screening for carriers of β-thalassemia and sickle cell disease. These services are still patchy and inadequate in many Arab countries recommending the upgrade of these services with strengthening of the education and training of health care providers and raising public awareness on the feasibility of prevention and care for haemoglobinopathies.

Efficient detection of Mediterranean β-thalassemia mutations by multiplex single-nucleotide primer extension

β-Thalassemias and abnormal hemoglobin variants are among the most common hereditary abnormalities in humans. Molecular characterization of the causative genetic variants is an essential part of the diagnostic process. In geographic areas with high hemoglobinopathy prevalence, such as the Mediterranean region, a limited number of genetic variants are responsible for the majority of hemoglobinopathy cases. Developing reliable, rapid and cost-effective mutation-specific molecular diagnostic assays targeting particular populations greatly facilitates routine hemoglobinopathy investigations. We developed a one-tube single-nucleotide primer extension assay for the detection of eight common Mediterranean β-thalassemia mutations: Codon 5 (-CT); CCT(Pro)->C–, Codon 6 (-A); GAG(Glu)->G-G, Codon 8 (-AA); AAG(Lys)->–G, IVS-I-1 (G->A), IVS-I-6 (T->C), IVS-I-110 (G->A), Codon 39 (C->T), and IVS-II-745 (C->G), as well as the hemoglobin S variant beta 6(A3) Glu>Val. We validated the new assay using previously genotyped samples obtaining 100% agreement between independent genotyping methods. Our approach, applicable in a range of Mediterranean countries, offers a combination of high accuracy and rapidity exploiting standard techniques and widely available equipment. It can be further adapted to particular populations by including/excluding assayed mutations. We facilitate future modifications by providing detailed information on assay design.

Immigration and changes in the epidemiology of hemoglobin disorders in Italy : an emerging public health burden

BACKGROUND

In the last years Italy is confronting with massive migratory movements from developing countries where hemoglobinopathies are widespread. This is causing a large diffusion and a changing spectrum in the epidemiology of hemoglobin disorders in Italy.

METHODS

Investigations recently published in Italy on hemoglobinopathies among immigrants were revised in order to appreciate the impact of immigration from developing countries on epidemiology of these pathologies and to outline adequate guidelines of prevention.

RESULTS

Although in Italy there is a limited number of investigations regarding the relation between immigration and hemoglobin disorders, published data show that in our Nation there is a changing and increasing spectrum of hemoglobinopathies linked to immigration.

CONCLUSIONS

Prospective and retrospective actions of public healthy preventive policy are requested, based upon information (health educational programs for immigrants and caregivers), screenings among immigrants (school screening, pre-marital, preconception and early pregnancy screening, newborn screening), counseling for foreign at-risk couples and healthy carriers.

Non-invasive prenatal diagnosis of beta-thalassemia and sickle-cell disease using pyrophosphorolysis-activated polymerization and melting curve analysis

OBJECTIVE

The aim of this study was to develop a pyrophosphorolysis-activated polymerization (PAP) assay for non-invasive prenatal diagnosis (NIPD) of β-thalassemia major and sickle-cell disease (SCD). PAP is able to detect mutations in free fetal DNA in a highly contaminating environment of maternal plasma DNA.

METHODS

Pyrophosphorolysis-activated polymerization primers were designed for 12 informative SNPs, genotyped by melting curve analysis (MCA) in both parents. The PAP assay was tested in a series of 13 plasma DNA samples collected from pregnant women. A retrospective NIPD was performed in a couple at risk for SCD.

RESULTS

All PAP reactions were optimized and able to detect <3% target gDNA in a background of >97% wildtype gDNA. In all 13 cases, the paternal allele was detected by PAP in maternal plasma at 10 to 18 weeks of gestation. For the couple at risk, PAP showed presence of the normal paternal SNP allele in maternal plasma, which was confirmed by results of the chorionic villus sampling analysis.

CONCLUSIONS

In contrast to other methods used for NIPD, the combined PAP and MCA analysis detecting the normal paternal allele is also applicable for couples at risk carrying the same mutation, provided that a previously born child is available for testing to determine the linkage to the paternal SNPs.

Decreased blood catalase activity is not related to specific beta-thalassemia mutations in Hungary

INTRODUCTION

Thalassemia erythrocytes are exposed to oxidative stress especially to hydrogen peroxide, which is regulated with the enzyme catalase. The aim of this study was to examine blood catalase activity and the relationship of blood catalase and beta-thalassemia gene mutations.

METHODS

Blood catalase activity, hemoglobin, HbA(2) , HbF, and beta-globin gene mutations were determined in 43 Hungarian patients with beta-thalassemia trait.

RESULTS

Compared to controls, the beta-thalassemia trait patients showed a low mean (P < 0.001) of blood catalase (men: 84 ± 29 MU/L vs. sex-matched controls: 118 ± 18 MU/L and women: 74 ± 18 MU/L vs. 108 ± 114 MU/L) and a low mean of blood catalase-to-blood hemoglobin ratio (men: 0.72 ± 0.22 MU/g vs. 0.85 ± 0.12 MU/g, women: 0.77 ± 0.26 MU/g vs. 0.84 ± 0.11 MU/g). The HbA(2) determination showed high sensitivity and specificity for the detection of beta-thalassemia trait patients. Mutation analyses revealed 13 beta-thalassemia trait mutations, of which six have not been reported before in Hungarian beta-thalassemia trait patients. Each group of mutations revealed decreased (P < 0.01) mean of blood catalase and catalase-to-hemoglobin ratio. Acatalasemia mutations were not found in beta-thalassemia trait patients.

CONCLUSION

The decrease in blood catalase activity might be due to the damaging effects of free radicals on the catalase protein. Consequently, these beta-thalassemia trait patients may be relatively susceptible to damage caused by oxidative stress.

Spectrum of β-thalassemia mutations in the eastern province of Saudi Arabia

β-Thalassemias comprise a group of heterogeneous hemoglobin (Hb) disorders characterized by the absence or reduced synthesis of the β-globin chain with a variable clinical presentation. The Al-Qatif and Al-Ahsa oases in the Eastern Province of Saudi Arabia are regions known for the high prevalence of these disorders. This study was conducted to provide a more precise picture of the β-thalassemia (β-thal) mutations prevalent in these regions and to estimate their frequencies. One hundred and 96 subjects with transfusion-dependent β-thalassemia (β-thal) disease were included in this study. A total of 14 β-thal mutations were identified with five mutations accounting for more than 80% of the total β-thal mutations identified. Of the 196 patients, 164 were homozygous for a β-thal mutation, while 32 were compound heterozygotes. We report here the novel identification of two mutations, namely, the Tunisian splice site IVS-I-130 (G→C) and the Mediterranean cryptic splice site IVS-I-110 (G→A), which have not been previously reported in the population of the Eastern Province. However, 15 patients (46.9%) with compound heterozygosities carried one of the β-thal mutations and the sickle cell mutation [Hb S or β6(A3)Glu→Val]. These patients were less frequently transfused than the patients who were homozygous for the β-thal mutations and presented with fewer complications. A more comprehensive overview of the genetic heterogeneity of the β-thal mutations in the Eastern Province of Saudi Arabia is presented in this article. This study will contribute to the establishment of an effective prevention program, including premarital screening.

Prenatal, noninvasive and preimplantation genetic diagnosis of inherited disorders: hemoglobinopathies

Disorders of hemoglobin synthesis have been used as a prototype for the development of most approaches for prenatal diagnosis (PND). PND for hemoglobinopathies based on molecular analysis of trophoblast or amniocyte DNA has accumulated approximately 30 years of experience. Disadvantages with conventional PND include 'invasive' fetal sampling and the need to terminate affected ongoing pregnancies. New developments are directed towards improving both the timing and/or safety of procedures. Preimplantation genetic diagnosis, an established procedure with 20 years of clinical application, avoids the need to terminate affected pregnancies through the identification and selective transfer of unaffected in vitro fertilization embryos. Approaches towards 'noninvasive' PND, through analyzing fetal cells or free fetal DNA present in the circulation of pregnant women, are a focus of ongoing research. Overall, PND, preimplantation genetic diagnosis (and potentially 'noninvasive' PND) represent valuable reproductive options for couples at risk of having a child affected with a severe inherited disease.

Health aspects of the pre-departure phase of migration

In the second article in a six-part PLoS Medicine series on Migration & Health, Brian Gushulak and Douglas MacPherson discuss the pre-departure phase of migration and the specific health risks and policy needs associated with this phase.

Current Genetic Epidemiology of β-Thalassemias and Structural Hemoglobin Variants in the Lazio Region (Central Italy) Following Recent Migration Movements

The aim of this study was to describe the changing pattern of mutational spectrum of β-thalassemia (β-thal) in the Lazio region (Central Italy), as consequence of recent demographic variations. From 1994 until present, 256 immigrant subjects with hemoglobin disorders (including 191 heterozygotes and 65 homozygotes or compound heterozygotes) coming from 44 different foreign countries, have been molecularly characterized. 14 β-globin gene mutations were identified and their frequencies reflect different ethnic origins: 8 of these mutations account for 76.97% of all molecular defects, while 6 of them are much rare, representing less than 2% of the total. These data differ, both in type and percentage, from the mutational spectrum detected in the native population in 1995. Since a few defects are prevalent in each country, a proper strategy for the identification of mutations in immigrant individuals relies on the prior knowledge of their frequency in native ethnic group.

Screening for clinically significant non-deletional alpha thalassaemia mutations by pyrosequencing

Non-deletional α(+)-thalassaemia is associated with a higher degree of morbidity and mortality than deletional forms of α(+)-thalassaemia. Screening for the common deletional forms of α-thalassaemia by Gap-PCR is widely practiced; however, the detection of non-deletional α-thalassaemia mutations is technically more labour-intensive and expensive, as it requires DNA sequencing. In addition, the presence of four very closely homologous alpha globin genes and the frequent co-existence of deletional forms of α-thalassaemia present another layer of complexity in the detection of these mutations. With growing evidence that non-deletional α-thalassaemia is relatively common in the UK, there is a demand for technologies which can quickly and accurately screen for these mutations. We describe a method utilising pyrosequencing for detecting the ten most common clinically significant non-deletional α-thalassaemia mutations in the UK. We tested 105 patients with non-deletional α-thalassaemia and found 100% concordance with known genotype as identified by Sanger sequencing. We found pyrosequencing to be simpler, more robust, quicker, and cheaper than conventional sequencing, making it a good choice for rapid and cost-effective diagnosis of patients with suspected non-deletional α-thalassaemia. The technique is also likely to help expedite prenatal diagnosis of pregnancies at risk of α-thalassaemia major.

Characterization of a novel deletion causing beta-thalassemia major in an Afghan family

We have identified and characterized a novel beta-globin gene deletion mutation in a family of Afghan ancestry. The proband was a 10-year-old transfusion-dependent female with the phenotype of beta-thalassemia major (beta-TM). DNA sequencing of the beta-globin gene showed no abnormalities. Multiplex ligation-dependent probe amplification (MLPA) showed reduced/absent probe height of the probe covering the 5' end of the beta-globin gene indicating a possible deletion. Gap-polymerase chain reaction (gap-PCR) produced junctional fragments and direct sequencing of the product revealed that the 5' breakpoint was 478 nucleotides upstream of the Cap site and the 3' breakpoint was in the second exon of the beta-globin gene, giving a deletion size of 909 bp. The proband was homozygous and the parents were heterozygous for the deletion. This is the first report of a large beta-thalassemia (beta-thal) deletion mutation in this ethnic group.

Molecular updating of β-thalassemia mutations in the Upper Egyptian population

We have updated the dataset of the molecular spectrum of the β-thalassemia (β-thal) in Upper Egypt. Buccal swabs were analyzed from 94 unrelated patients with β-thal major (β-TM) using reverse dot-blot and multiplex amplification refractory mutation system-polymerase chain reaction (ARMS-PCR). The most frequent mutation was IVS-I-110 (G>A) (57%). The IVS-I-110, IVS-I-6 (T>C) and IVS-I-1 (G>A) mutations accounted for 87% of the β-thal anomalies. The codon 39 (C>T) and frameshift codon (FSC) 6 (-A) (GAG>-GG) mutations were only detected in Al-Minya and Qina, respectively. We did not observe the IVS-II-745 (C>G) or -101 (C>T) mutations. Forty-three percent of Upper Egyptians were homozygotes. Our efforts were an important step to complete the mutation map of β-thal in Egypt restricted to Cairo and the Nile Delta regions. This study will help to develop preventative programs for Upper Egyptians. It addressed the genetic drift of the β-thal gene mutations in Africa, Asia, and Europe.