Reliability of hemoglobin A2 value as measured by the Premier Resolution system for screening of ß-thalassemia carriers.

OBJECTIVES: Accurate quantification of hemoglobin (Hb) A2 is vital for diagnosing ß-thalassemia carriers. This study aimed to assess the precision and diagnostic utility of HbA2 measurements using the new high-performance liquid chromatography (HPLC) method, Premier Resolution, in comparison to capillary electrophoresis (CE). METHODS: We analyzed 418 samples, previously identified as A2A by CE, using Premier Resolution-HPLC. We compared the results, established correlations, and determined an optimal HbA2 cutoff value for ß-thalassemia screening. Additionally, we prospectively evaluated the chosen cutoff value in 632 samples. Mutations in the ß- and α-globin genes were identified using polymerase chain reaction (PCR) techniques and DNA sequencing. RESULTS: HbA2 levels were consistently higher with Premier Resolution, yet there was a significant correlation with CE in all samples (bias, -0.33; r, 0.991), ß-thalassemia (bias, -0.27; r, 0.927), and non-ß-thalassemia carriers (bias, -0.36; r, 0.928). An HbA2 cutoff value of ≥4.0 % for ß-thalassemia screening achieved 100 % sensitivity and 99.6 % specificity. Further validation yielded sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 97.3 , 99.8, 97.3, 99.8, and 99.7 %, respectively. We also identified a rare ß-Hb variant, Hb La Desirade [HBB:c.389C>T], associated with ß-thalassemia and co-inherited with a single α-globin gene. CONCLUSIONS: The Premier Resolution HPLC is a reliable and accurate method for routine ß-thalassemia carrier screening, aligning with existing CE methods.

A New δ-Globin Gene Variant: Hb A2-Yulin [δ46(CD5)Gly→Arg,HBD: C.139G > A].

We report a new δ-chain hemoglobin (Hb) variant observed in a 5-year-old female living in Yulin, Guangxi, China. Capillary electrophoresis revealed splitting of the Hb A2 peak into two fractions (Hb A2 and Hb A2 variant), and the Hb A2 variant was also detected by high-performance liquid chromatography. However, it could not be detected using matrix-assisted laser desorption lonization-time of flight mass spectrometry. CD41-42 (-TCTT) heterozygosity was observed on the HBB gene by PCR and reverse dot-blot hybridization. Sanger sequencing showed a new transition (G > A) at codon 46 of the HBD gene, resulting in glycine changing to arginine. Based on the patient's place of residence, the new variant was named Hb A2-Yulin [δ46(CD5)Gly→Arg,HBD:c.139G > A].

A Novel Frameshift Mutation(HBA2:C.337delC) Associated With α-Thalassemia Trait Detected by Next-Generation Sequencing in Southern China.

Here, we report a novel frameshift mutation caused by a single base deletion in exon 3 of the HBA2 gene (HBA2:c.337delC) detected by next-generation sequencing. The proband was a 26-year-old Chinese pregnant woman who originates from Hunan Province. Her mean corpuscular volume(MCV) and mean corpuscular hemoglobin (MCH) had a mild decrease. Capillary electrophoresis (CE) showed that both Hb A (97.8%) and Hb F (0.0%) values were within normal range, while the Hb A2 (2.2%) value was below normal. Sequence analysis of the α and ß-globin genes revealed a novel single base deletion at codon 112 (HBA2:c.337delC) in the heterozygous state, which resulted in a mild phenotype of α-thalassemia.

Molecular Characterization of Haemoglobin E.

OBJECTIVE: To detect mutation in cases having haemoglobin A2 level >7% on high performance liquid chromatography. METHODS: The cross-sectional, descriptive study was conducted from July 2017 to December 2018 at the Department of Haematology and Human Genetics and Molecular Biology, University of Health Sciences, Lahore, Pakistan, and comprised patients of either gender with haemoglobin A2 ≥7%. The samples were collected from different cities of Punjab in collaboration with the Punjab Thalassemia Prevention Programme, Lahore. The samples were subjected to complete blood count and high performance liquid chromatography using automated haematology analysers and variant-II beta thalassemia short programme, respectively. To analyse haemoglobin E mutations at the molecular level, polymerase chain reaction-restriction fragment length polymorphism (PCR_RFLP) was performed using a type IIS restriction endonuclease known as Mnl1 (derived from Moraxella nonliquefaciens) to cleave DNA at specific sites and the results were further confirmed on randomly selected samples using Sanger sequencing. Data was analysed using SPSS 25. RESULTS: Of the 39 patients, 15(38.5%) were males and 24(61.5%) were females. The overall median age was 14 (23) years. There were 29 (74.4%) patients with thalassemia family history, and 22(56.4%) had a positive family history of transfusion related to thalassemia, while no patient had a family history of iron therapy. The median haemoglobin A, haemoglobin A2 and haemoglobin F levels were 72.2 (65.2-79.1) %, 26.6 (19.1-34.0) % and 0.9 (-0.8-2.6) %, respectively. After molecular investigation, HbAE mutation was found in 23(59%) patients, while wild type HbAA genotype was found in 16(41%). The heterozygous HbE mutation was present in 23(59%) patients. CONCLUSIONS: Frequently missed/undiagnosed cases of haemoglobin E that co-elute with haemoglobin A2 in the same high performance liquid chromatography window were detected among those with haemoglobin A2 ≥7%.

Does size matter? Two new deletions in the HBB gene cause ß0-thalassemia.

Most ß-thalassemias are caused by mutations involving one or a limited number of nucleotides within the gene or its adjacent regions. They can be substitutions or deletions; in these cases, the loss ranges from a single nucleotide to even the entire HBB gene, so we wonder if the phenotype is due to the size of the deletion or the location of the mutation. To clarify this, we present two new deletions in the ß-globin gene that cause ß0-thalassemia. The hematological parameters were determined with an automated cell counter; the Hb A2 and Hb F levels were measured by performance liquid chromatography. Hemoglobins were analyzed by capillary zone electrophoresis (Sebia Capillarys Flex system) and ion-exchange HPLC (BioRad Variant II ß-thalassemia Short Program). Molecular characterization was performed by automatic Sanger sequencing. The screening of common α-thalassemia point mutations and deletions in the world (21 in total) were carried out using multiplex PCR followed by reverse-hybridization with a commercial Alpha-Globin StripAssay kit. We have characterized two new mutations-(1) 1-bp deletion [CD61/62(-G)] [HBB:c.186_187delG], (2) 105-bp deletion [IVS-2-nt767-CD111] [HBB:c.316-84_333del]-and we have described, for first time in Spain, the 25-bp deletion [ß nts 252 - 276 deleted] [HBB:c.93-22_95del] mutation. These mutations were classified as pathogenic by UniProt Variants confirmed according to the American College of Medical Genetics and Genomics guidelines. These mutations present a phenotype compatible with ß0-thalassemia, supported by hematological parameters that correlate the degree of reduction in the synthesis of the ß-globin chain. Identification of this type of mutation is important for genetic counselling of partners where both are carriers, so that they are aware of the genetic risk of having affected children, allowing them to take an informed decision about their reproductive choices.

A New Mutation, Hb A2-Canakkale [δ10(A7)Ala→Val; HBD: c.32C>T], and Other Well-Known δ Variants Identified in a Selected Cohort with Low Hb A2 Levels.

Hemoglobinopathies are the most common single-gene disorders, and ß-thalassemia (ß-thal) imposes a tremendous health burden on Turkey. Thus, premarital carrier screening is obligatory in Turkey, as it is in some other countries. As a result of this mandatory procedure, at routine clinical checkups, many individuals who had undergone premarital screening but did not have any clinical symptoms and/or hematological findings, have compulsorily been required to undergo further evaluation due to abnormal levels of hemoglobin (Hb) fractions (Hb A, Hb A2 and Hb F). Many consequences, such as mutations in unrelated gene(s) or someone's nutritional status, have been reported to affect the Hb fractions levels. In the present study, we aimed to determine whether HBD has a molecular causative role in patients with low Hb A2 levels (below 1.8%). The study was conducted with 20 individuals with low Hb A2 levels who had applied to our outpatient clinic. All DNA samples were analyzed for the HBD gene. Nineteen of the 20 subjects were diagnosed to carry a mutation with one of four different δ-globin variants. Three of them had been described previously [Hb A2-Yialousa (HBD: c.82G>T), Hb A2-Bornova (HBD: c.350G>C) and Hb A2-Yokoshima (HBD: c.77G>A)]. The novel [δ10(A7)Ala→Val, HBD: c.32C>T] mutation was defined as a new δ variant and reported to the HbVar database as Hb A2-Canakkale. In conclusion, the molecular characterization of Hb A2 low levels has been suggested to be significant for a definite diagnosis and counseling.

A Triple-Heterozygous ß-Thalassemia Patient Demonstrated an Unusual Electrophoresis Pattern Due to a Novel ß0 Mutation [an IVS-II-654 (C>T) mutation with a Hb Zürich-Langstrasse (HBB: c.151A>T) mutation in cis].

ß-Thalassemia (ß-thal) is caused by mutations on the ß-globin genes, causing reduced (ß+) or absent (ß0) synthesis of the ß chains of hemoglobin (Hb). In this report, a 28-year-old male patient with anemia and jaundice, was diagnosed with triple-heterozygous ß-thal [an IVS-II-654 (C>T) mutation, a Hb Zürich-Langstrasse (HBB: c.151A>T) mutation and a Hb G-Siriraj (HBB: c.22G>A) mutation] by gene sequencing. However, his electrophoresis pattern was unusual: 90.8% Hb G-Siriraj, 5.9% Hb A2, 3.3% Hb F, no Hb A, no Hb Zürich-Langstrasse. His mother carried a ß-thal trait (ßA/ßIVS-II-654) having mild anemia, with a classical electrophoresis pattern (95.1% Hb A, 4.4% Hb A2, 0.5% Hb F). His father was heterozygous for Hb G-Siriraj (ßA/ßG-Siriraj) but asymptomatic, with a corresponding electrophoresis pattern (63.9% Hb A, 3.5% Hb A2, 32.6% Hb G-Siriraj). In view of the family study results, the Hb Zürich-Langstrasse mutation in the proband was considered a de novo mutation occurring on the ßIVS-II-654 allele that he inherited from his mother, resulting in a ßIVS-II-654/Hb Zürich-Langstrasse genotype, which should be interpreted as a novel ß0 mutation. This report illustrates that mutations in cis can confound genotype-phenotype correlations, therefore, just as DNA testing and Hb analysis, family study is also indispensable to the accurate identification of ß-thal mutations.

[The value of combined detection of HbA2 and HbF for the screening of thalassemia among individuals of childbearing ages].

OBJECTIVE: To assess the application value of combined detection of HbA2 and HbF for the screening of thalassemia among a population of childbearing age in Quanzhou, Fujian, and determine the optimal cut-off values for the region. METHODS: Capillary hemoglobin electrophoresis and genetic testing for α and ß globin gene mutations were simultaneously carried out on 11 428 patients with suspected thalassemia. Statistical methods were used to analyze the distribution of various types of thalassemia and compare the performance of HbA2 and HbF measurement for the screening of various types of thalassemia. The optimal cut-off values for HbA2 and HbF were determined with the ROC curves. RESULTS: 4591 patients with α, ß, and αß compound thalassemia were identified by genetic testing. The most common genotypes for α and ß thalassemia included --SEA/αα and ß654/ßN, ß41-42/ßN, and ß17/ßN. The ROC curves were drawn to compare the performance of HbA2 screening for α-, ß-, αß-compound, static α-, mild α-, and intermediate α-thalassemia, and the maximum area under the curves was 0.674, 0.984, 0.936, 0.499, 0.731, 0.956, and the optimal cut-off values for HbA2 were 2.45%, 3.25%, 3.65%, 2.95%, 2.55%, 1.75%, respectively. CONCLUSION: HbA2 is an efficient indicator for identifying intermediate types of α-, ß-, and αß compound thalassemia. The combination of HbA2 and HbF measurement can effectively detect carriers for ß-thalassemia mutations.

δ-Hemoglobinopathies in Thailand: screening, molecular basis, genotype-phenotype interaction, and implication for prevention and control of thalassemia.

The δ-globin gene defects are clinically silent but interaction with ß-thalassemia can lead to a misdiagnosis of ß-thalassemia carrier. We report an extensive molecular characterization of δ-hemoglobinopathies in Thailand. Study was done on 32,108 subjects, encountered at the thalassemia screening. Six different approaches based on the reduced Hb A2 or appearance of Hb A2-derivative were established for selective recruitment of subjects. Among 32,108 subjects, a total of 296 subjects were suspected of having δ-globin gene defects. Of these 296 subjects, Hb and DNA analyses identified δ-hemoglobinopathies with 10 different mutations in 34 (0.11%) of them. These included a novel mutation, [δCD30(AGG>GGG) (n = 1)], 5 previously undescribed in Thailand, [δ-44(G>A) (n = 7), Hb A2-Troodos (n = 5), δIVSII-897(A>C) (n = 4), δ-68(C>T) (n = 2), and Hb A2-Indonesia (n = 1)], and 4 mutations previously found in Thailand, [Hb A2-Melbourne (n = 9), δ-77(T>C) (n = 3), Hb A2' (n = 1), and Hb A2-Kiriwong (n = 1)]. Genetic heterogeneities seen included interactions of δ-globin gene defects with heterozygous Hb E, ß-thalassemia, α-thalassemia, and in cis locations of the Hb A2-Troodos and Hb E mutations found for the first time. Rapid identification methods of these δ-globin gene mutations were developed. The results should prove useful to a prevention and control program of hemoglobinopathies in the region.

Analysis of δ-globin gene alleles in Tunisians: description of three new delta-thalassemia mutations.

BACKGROUND: Thalassemia is one of the most prevalent worldwide autosomal recessive disorders characterized by a great molecular and clinical expression heterogeneity. Alpha and beta-thalassemia are the main two types observed in case of mutations affecting alpha and beta-globin genes respectively. Delta-thalassemia is noted when mutations occur on the delta-globin gene. In Tunisia, ß-thalassemia prevalence is estimated at 2.21% of carriers. However, few reports investigated the delta-globin gene. OBJECTIVES: In this work, we aimed to perform a molecular study to help define the molecular spectrum of δ-thalassemia mutations in Tunisia. PATIENTS AND METHODS: The study involved 7558 patients among whom we selected 179 individuals with abnormal HbA2 values or fractions. Hemoglobin analysis was performed using Capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC). DNA sequencing was performed on ABI prism 310 Genetic Analyzer Applied Biosystems. CUPSAT (Cologne University Protein Stability Analysis Tool) was used for the prediction of protein stability changes upon missense mutations and mutants were modeled via DeepView-SwissPdbViewer and POV-Ray softwares for molecular dynamics simulation studies. RESULTS: We identified four mutations: HbA2-Yialousa described for the first time in Tunisia ( in 72.72% of cases) and 3 mutations reported for the first time in the world: (i) c.442 T > C Stop147Arg ext 15aa-stop observed in 18.18% of cases, (ii) c.187 G > C (Ala62Pro) noted in 4.54% of cases and (iii) c.93-1G > C found in 4.54% of cases. CONCLUSION: Our data provide genetic basis that would be especially useful in screening for beta-thalassemia trait during delta-beta thalassemia associations.

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

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

A New Hemoglobin Variant: Hb Jiujiang [α18(A16)Gly→Cys, HBA2: c.55G>T].

We have identified a new α chain hemoglobin (Hb) variant in a Chinese subject. Sequencing of the α-globin gene revealed a mutation in exon 1 at nucleotide 55, which results in the replacement of a glycine by cysteine at codon 18 [α18(A16)Gly→Cys, HBA2: c.55G>T] that we have named Hb Jiujiang for the region of origin of the proband.

Eleven Cases of Hb J-Paris-I [HBA2: c.38C>A (or HBA1)]: A Stable α Chain Variant Elutes in the P3 Window on High-Performance Liquid Chromatography.

Hb J-Paris-I [HBA2: c.38C>A (or HBA1)] is a stable fast-moving hemoglobin (Hb) that elutes in the P3 window on high performance liquid chromatography (HPLC). The mutation can happen on either the α1- or α2-globin gene. Codon 12 changes from GCC to GAC to replace the alanine amino acid with aspartic acid. This change is external with no clinical significance. The elution in the P3 wave on HPLC can interfere with the glycated Hb assay by HPLC. In this study, data of 11 cases of Hb J-Paris-I were thoroughly presented. The majority of the cases were of Indian ethnicity. The mean value of Hb J-Paris-I on HPLC was 26.7 ± 2.0%. The retention time (RT) was 1.75 ± 0.03 min. The isoelectric focusing (IEF) mean value was -5.6 (range -6.1 to -4.9). Hb A2 was consistently reduced to 1.8 ± 0.3%. A fraction of 0.8% corresponding to the Hb A2-J-Paris-I (α2J-Paris-Iδ2) is likely to be concealed within the A0 peak of Hb A on HPLC. Interestingly, two cases were associated with two different polymorphisms [HBA2: c.-24C>G or Cap +14 (C>G) and HBA2: c.*136A>G polymorphism] without apparent effect on the variant expression.

An Evaluation for the Causes of Reduced Hb A2 and the Molecular Characterization of HBD Variants in Hong Kong.

Prenatal screening of ß-thalassemia (ß-thal) carriers is based on the hallmark phenotype of microcytosis and raised Hb A2. The unanticipated birth of ß-thal major (ß-TM) offspring to ß-thal carriers who were misdiagnosed during prenatal screening have been reported. A subset of these resulted from the masked phenotype due to the coinheritance of HBD variants. In a broader sense, the causes of reduced Hb A2 in thalassemia screening, the prevalence and spectrum of HBD variants in Hong Kong remain to be characterized. Over a 13-month period, a total of 2982 samples were referred for thalassemia screening. Surplus samples with reduced Hb A2 levels (2.0%) were evaluated. HBD variations were assessed by direct sequencing. Sixty-six samples were tested. Hb H disease, HBD variants, α-thalassemia (α-thal) trait and iron deficiency were detected in 40 (60.6%), 12 (18.2%), eight (12.1%) and seven (10.6%) samples, respectively. Seven samples carried more than one of the mentioned conditions. The cause remained elusive in seven samples. Thirteen HBD variants were detected and two were recurrent, including HBD: c.-127T>C [-77 (T>C)] and HBD: c.314G>A (Hb Chori-Burnaby). A novel nonsense variant HBD: c.262C>T [codon 87 (C>T)] was detected in cis with HBD: c.-127T>C. Overall, the prevalence of HBD variants was 0.4%. This study advanced our understanding of the causes of reduced Hb A2 in clinical practice and identified hereditary disorders of α- and δ-globin genes as the prevailing causes. It established the landscape of HBD variations in our locality and highlighted the pitfall of phenotypic screening of ß-thal carriers.

Heterozygosity for the Novel HBA2: c.*91_*92delTA Polyadenylation Site Variant on the α2-Globin Gene Expanding the Genetic Spectrum of α-Thalassemia in Iran.

There are four copy numbers of α-globin genes (16p13.3) in the human genome and the number of defective α-globin genes dictates the severity of α-thalassemia (α-thal). Mutations that occur in the 3' untranslated region (3'UTR), and especially at the polyadenylation (polyA) sites, affect the translation, stability and export of mRNA. A patient with hypochromic microcytic anemia was referred to the Kariminejad-Najmabadi Pathology & Genetics Center, Tehran, Iran by the health network. Molecular analysis of genomic DNA for the evaluation of mutations on the α- and ß-globin genes was performed. Direct sequencing of the hemoglobin (Hb) subunit α2 (HBA2) gene revealed a two nucleotide deletion between +816 and +817 in the 3'UTR, located at the polyA site, which seems to be a novel pathogenic variant. This novel variant expands the genetic spectrum of α-thal in the 3'UTR of the HBA2 gene.

Hb A2-Pistoia [δ89(F5)Ser→Asn, HBD: c.269G>a]: a Novel Mutation on the δ-Globin Gene in an Italian Child.

We describe a new hemoglobin (Hb) variant, found in a 6-year-old Italian male living in Pistoia, Italy. An abnormal pattern compatible with a Hb A2 variant was observed on capillary electrophoresis (CE); direct sequencing revealed a transition at codon 89 of the δ gene (HBD: c.269G>A) changing serine into asparagine. The variant was also identified as Hb A2-Pistoia according to the traditional nomenclature and no other globin defect was present. The observation and description of this Hb A2 variant contributes to the number and heterogeneity of mutations of the δ-globin gene in the Mediterranean Area.

Diagnosis and Prenatal Diagnosis in a Chinese Family Carrying the Rare α-Thalassemia Gene HBA2: c.1A>G Mutation.

The aim of this study was to identify the rare thalassemia genotype in a family and perform prenatal diagnosis (PND) on the proband's unborn child. Peripheral blood was collected from the family members for hematology analysis and capillary electrophoresis (CE) analysis. Peripheral blood and cord blood were analyzed by gap-polymerase chain reaction (gap-PCR), reverse dot-blot and Sanger sequencing for genotypes of α-thalassemia (α-thal). A heterozygous mutation, HBA2: c.1A>G, was identified in the proband and his father. Two compound heterozygous variants, HBA2: c.1A>G and the - -SEA (Southeast Asian) deletion, were revealed in the proband's unborn child. The hemoglobin (Hb) CE result of the fetal cord blood indicated the fetus had Hb H disease. We have identified a rare thalassemia mutation (HBA2: c.1A>G) in a Chinese family and enriched the rare α-thal gene pool in the Chinese population. When the patient's phenotype does not match the genotype detected by thalassemia gene detection kits, further investigation of rare genotypes should be conducted to avoid missed diagnosis or misdiagnosis, which can help guide clinical diagnosis, population screening and genetic counseling.

Nondeletional α-Thalassemia: Two New Mutations on the α2 Gene.

About 10.0% of α-thalassemia (α-thal) cases are due to point mutations, small deletions, or insertions of one or more bases on the α genes that can alter mRNA processing at the transcription, translation, or post-translation level; these cases are called nondeletional α-thalassemias (α-thal). Most occur within the domain of the α2 gene without changes in the expression of the α1 gene. We present two new frameshift mutations on the HBA2 gene, associated with a nondeletional α-thal phenotype. The probands were referred to our clinic because of persistent microcytosis and hypochromia. The molecular characterization was performed by automatic sequencing of the α-globin genes. Two new mutations were detected on the HBA2 gene; HBA2: c.85delG, p.(Ala29fs*21), and HBA2: c.268_280delCACAAGCTTCGGG, p.(His90Trpfs*9). These new mutations cause a change of the reading frame, the first on codon 28 and the second from codons 89 to 93. In the first mutation, the result is an altered amino acid sequence and a premature termination codon at position 87, while the elimination of 13 bp generates a protein of 95 residues and in this case, the premature termination codon is at position 96. These types of mutation are among the most damaging changes to the coding of a protein. Not only do they lead to changes in the length of the polypeptide, but they also vary the chemical composition, which would result in a nonfunctional protein. The importance of identifying these new mutations lies in their possible association with α0-thal, which could lead to a severe thalassemia.

A Woman with Missing Hb A2 Due to a Novel (εγ)δß0-Thalassemia and a Novel δ-Globin Variant Hb A2-Gebenstorf (HBD: c.209G>A).

A woman completely lacking Hb A2 on the high performance liquid chromatography (HPLC) analysis, presented with a novel deletional (εγ)δß0-thal and a δ-globin gene variant. This combination causes a ß-thalassemia (ß-thal) minor phenotype. The woman was referred by a hematologist due to abnormal blood counts. Multiplex ligation-dependent probe amplification (MLPA) and microarray analysis showed a heterozygous, 177 kb long deletion that removed the locus control region enhancer plus the ε, Gγ and Aγ genes. Additional sequencing revealed a novel variant HBD: c.209G>A, p.Gly70Asp in the heterozygous state, called Hb A2-Gebenstorf. The combination of the two variants explains the lack of Hb A2 in this woman.

α-Globin Genotypes Associated with Hb H Disease: A Report from Oman and a Review of the Literature from the Eastern Mediterranean Region.

α-Thalassemia (α-thal) is the most common autosomal recessive hemoglobinopathy. There is a vast diversity and geographical variability in underlying genotypes in Hb H (ß4) patients. Herein, we describe the genotypes found in the largest report of Omani Hb H patients. Moreover, we reviewed and summarized the literature published from the Eastern Mediterranean region. A retrospective review of all genetically confirmed Hb H disease patients diagnosed between 2007 and 2017 at Sultan Qaboos University Hospital, Muscat, Oman, was performed. Hematological parameters and clinical presentations were assessed. Both α-globin genes were screened for deletional and nondeletional mutations using a stepwise diagnostic strategy as described before. A total of 52 patients (27 females and 25 males) with a mean age of 20.6 years (range 0.23-80.0) were molecularly confirmed to carry Hb H disease. The patients had a hemoglobin (Hb) level of 9.3 g/dL (range 5.7-13.0) and mean corpuscular volume (MCV) of 58.4 fL (range 48.2-82.1). A total of eight genotype combinations were identified, with α2 polyadenylation signal mutation (polyA1) (AATAAA>AATAAG (αPA1α/αPA1α), often cited as αT-Saudiα/αT-Saudiα, being the most common (53.8%) followed by -α3.7/- -MED I (28.8%). Our cohort also included patients with combinations of αPA1 with other Hb variants: αPA1α/αPA1α with Hb S (HBB: c.20A>T) trait (n = 2), -α3.7/αPA1α (n = 2) and αcodon 19α (HBA2: c.56delG)/αPA1α (n = 1). Nondeletional Hb H disease due to the αPA1 mutation is the most common in Omanis. Molecular diagnosis is necessary for accurate confirmation of the diagnosis of α-thal, determination of underlying genotypes, follow-up and counseling.