The Oxygen Affinity of Haemoglobin E

Oxygen dissociation studies were carried out on haemoglobin E (Hb E) at both high and low haemoglobin concentrations. Oxygen affinities of fresh red cells from three people homozygous for Hb E and from one with Hb E-beta thalassaemia (Hb-E trait/beta-thal trait) were low in three out of four patients studied, while the oxygen affinity of red cells from an individual with Hb-E was normal 2,3-DPG concentration in the fresh cells from the people with homozygous Hb E or Hb-E trait/beta-thal trait which showed low oxygen affinities were elevated sufficiently to account for the shifts observed. When the cells from two of these people with homozygous Hb E were depleted of 2,3-DPG. their oxygen affinities became the same as that of similarly treated normal cells. Pure 'stripped' Hb E in dilute solution behaved identically to Hb A in respect of P50, Bohr shift, haem-haem interaction, and interaction with inorganic phosphate or 2,3-DPG. Hb E, therefore, has the same oxypgen dissociation properties as Hb A both in dilute solution and in the red cell. The low oxygen affinities found in the fresh cells and in whole blood are caused by high 2,3-DPG concentrations within the cell.     

The Oxygen Affinity of Haemoglobin Hammersmith

Oxygen dissociation studies were carried out on red cells and lysates from a patient heterozygous for Hb Hammersmith. The oxygen affinity of the cells at pH 7.1 was decreased, partly by an increased cellular concentration of 2,3-DPG and more importantly by an intrinsic low affinity of Hb Hammersmity. Haem-haem interactions were reduced and an abnormal Bohr effect (pH 7.1-7.4) was found in the cells which would bring about an additional decrease in oxygen affinity at physiological pH. Oxygen dissociation studies on the lysates showed a low oxygen affinity, a normal Bohr effect at 50% saturation, slightly decreased haem-haem interactions and a normal interaction with 2,3-DPG. Estimation of the percentage of Hb Hammersmith in the lysates of the patient's cells by selective precipitation of the abnormal beta chain with p-chloromercuribenzoate (PCMB) showed the presence of 30-33% abnormal haemoglobin. Assuming no interaction between the Hb A and the Hb Hammersmith, oxygen dissociation curves were calculated for Hb Hammersmith alone and these indicated that it has greatly decreased oxygen affinity, a normal Bohr effect, normal 2,3-DPG interaction and (somewhat) decreased haem-haem interactions.     

The Concentration Dependence of the Oxygen Affinity of Haemoglobin S

The effect of the concentration of haemoglobin S (Hb S) on its oxygen-dissociation properties was studied using either reconstituted Hb-S cells of different mean corpuscular haemoglobin concentrations (MCHCs) prepared by osmotic lysis, or cells in which Hb S is diluted by the presence of another haemoglobin. Only 4% (phosphate buffer) and 21%(bis Tris) of the low oxygen affinity of fresh Hb-S cells was found to be due to their slightly elevated intracellular 2,3-DPG concentrations since when the cells were depleted of 2,3-DPG most of the low affinity remained. The low affinity showed a marked dependence upon haemoglobin concentration which was absent for 2,3-DPG-depleted Hb-A cells and, by extrapolation, the MCHC at which the oxygen affinities of the Hb-S cells became identical to that of the Hb-A cells was 14.5 g/dl in phosphate buffer and 13.1 g/dl in bis Tris. Both fresh and 2,3-DPG-depleted cells containing another haemoglobin as well as Hb S (Hb-SA, Hb-SC and Hb-SF cells) were also found to have low oxygen affinities provided that the intracellular Hb-S concentration(MC(Hb-S)C) was above a certain level. These also showed a strong dependence upon the MC(Hb-S)C. The mean MC(Hb-S)C at which the low oxygen affinities of the DPG-depleted cells were abolished were 8.3 g/dl (phosphate) and 11.2 g/dl (bis Tris). Hb F in fresh Hb-SF cells brought about a much greater increase in oxygen affinity than the same amount of either Hb A or Hb C. In 2,3-DPG depleted cells Hb A showed a greater ability to 'dilute' the Hb S than did Hb C. The conditions for the low oxygen affinity of Hb S were therefore found to be very similar to those required for the gelling of both pure Hb S, and Hb S in haemoglobin mixtures. It was concluded therefore that the low oxygen affinity of the Hb S was caused by the polymerization and that the difference between the oxygen affinities of Hb-S and Hb-A cells may be used as a measure of the polymerization process.     

Inherited Hemoglobin Disorders in Guinea-Bissau,West Africa: A Population Study

The determination of the prevalence of inherited hemoglobin (Hb) disorders in endemic areas is important in order to develop programs for their control and management. The aim of this study is to determine the prevalence of inherited Hb diseases in Guinea-Bissau which is situated on the west coast of Africa, between Senegal and Guinea. One thousand and fifty-seven blood samples were collected and analyzed with high performance liquid chromatography (HPLC) for detection of β-thalassemia (thal) and Hb variants, and by gap polymerase chain reaction (gap-PCR) for the detection of deletions in the α-globin genes. We found 4.7% children were heterozygous for Hb S [β6(A3)Glu→Val, GAG →GTG], 0.2% were homozygous for Hb S, and 0.3% were heterozygous for Hb C [β6(A3)Glu→Lys, GAG →AAG]. One child had heterozygous β⁺-thal, 13.8% were heterozygous for the ?α^3.7 deletion, 1.5% were homozygous for the ?α^3.7 deletion, and 1.5% were heterozygous for the ?α^4.2 deletion. We recommend national screening programs to focus primarily on sickle cell disease, since β-thal is rare, and the observed α-thal deletions are of minor genetic importance.     

Co‐inheritance of Hb Hershey [β70(E14) Ala→Gly] and Hb La Pommeraie [β133(H11)Val→Met] in a Sicilian subject

Objectives: This report represents the first observation in Sicily of two rare β‐globin gene variants, Hb Hershey [β70(E14) Ala→Gly] and Hb La Pommeraie [β133(H11)Val→Met], found in a 35‐year‐old male patient from Messina, in the north‐east of Sicily during population screening for hemoglobinopathies. Methods: The occurrence of the Hb variants was assessed by cation exchange chromatography while complete blood counts were obtained using automatic cell counters. Red cell lysates were analyzed by electrophoresis at alkaline and acid pH. Stability of hemoglobin was checked by the isopropanol precipitation test and by the heat tests while inclusion bodies and reticulocyte count were determined by incubation of blood samples with brilliant cresyl blue. Molecular analysis was performed by DNA sequencing of β‐ and α‐globin genes. Results: We observed an abnormally high performance liquid chromatography elution with a slight reduction in mean corpuscular volume and mean corpuscular haemoglobin parameters and mutations at codon 70 G C C→G G C (Hb Hershey) and at codon 133 G TG→ A TG (Hb La Pommeraie) in β‐globin gene. Conclusion: Family analysis of three generations demonstrated the presence of these two mutations in trans. So it was possible to describe the phenotypes of these variants in a heterozygous state and in double heterozygous state.     

Hb Memphis [HBA2: c.70G>C (or HBA1)] in a Turkish Child: A Case Report and Comparison to Hb Q-Thailand (HBA1: c.223G>C)

Hb Memphis [α23(B4)Glu→Gln; HBA2: c.70G?>?C (or HBA1)] is a stable hemoglobin (Hb) variant caused by a substitution of glutamine for glutamic acid at residue 23 of the α2- or α1-globin chain. Heterozygous Hb Memphis has no known clinical or hematological effect, and all prior reports have resulted from observations in persons of African descent with sickle cell disease and an unusually mild clinical course. Family studies suggest that Hb Memphis may modulate sickling. Only brief characterizations of Hb Memphis trait in the absence of Hb S are present in the current literature. We report isolated Hb Memphis trait in Turkish individuals in whom the initial laboratory incorrectly identified the α variant as Q-Thailand [α74(EF3)Asp→His; HBA1: c.223G?>?C]. In one case, a heterozygous ?3.7?kb α gene deletion was also present, which increased the variant Hb level to a percentage similar to that of the more common Hb Q-Thailand, which may have led to the misidentification. Herein, we discuss the characterization and comparison of these variants and underscore the necessity of confirming characterization by more than one method prior to assigning Hb variant identification.     

The Hb Tarrant [α126(H9)Asp→Asn] Mutation is Localized in the α2-Globin Gene

Hb Tarrant [αl26(H9)Asp→Asn] is an abnormal variant with high oxygen affinity and decreased cooperativity in the absence of 2,3-diphosphoglycerate (2,3-DPG) and a normal Bohr effect (1,2). At room temperature, it migrates close to Hb F on cellulose acetate electrophoresis at pH 8.6 and shows a hybrid formation at 4°C (1,3). The biochemical studies showed a substitution of asparagine for aspartic acid at codon 126 in the α chain; this substitution suggested a GAC→AAC transition at an undefined α-globin gene (1-4). Hb Tarrant was previously detected in four families with Mexican ancestors, but molecular studies were not performed (2-4).     

Red Cell 2,3-Diphosphoglycerate Levels in Children with Hereditary Haemolytic Anaemias

The role of red cell 2,3-diphosphoglycerate (2,3-DPG) in increasing the availability of haemoglobin oxygen in neonatal jaundice and hereditary haemolytic anaemias was investigated. Measurements of 2,3-DPG were carried out on 58 normal children and six normal adults, 18 full-term newborns with neonatal jaundice and 57 cases (51 children and six adults) with hereditary haemolytic anaemias. In normal children and adults, with a mean haemoglobin of 12.69 g/dl, mean 2,3-DPG was 14.90 mumol/g Hb. In jaundiced newborns with a mean haemoglobin of 16.04 g/dl mean 2,3-DPG levels were 14.51 mumol/g Hb, i.e. normal. 2,3-DPG levels were increased in patients with beta-thalassaemia major, alpha-thalassaemia, sickle-cell disease, favism, hereditary spherocytosis and in heterozygotes for beta-thalassaemia with increased haemoglobin F. In heterozygotes for beta-thalassaemia with increased haemoglobin A2 only and in sickle cell trait 2,3-DPG levels were normal.     

GBT440 increases haemoglobin oxygen affinity,reduces sickling and prolongs RBC half‐life in a murine model of sickle cell disease

A major driver of the pathophysiology of sickle cell disease (SCD) is polymerization of deoxygenated haemoglobin S (HbS), which leads to sickling and destruction of red blood cells (RBCs) and end‐organ damage. Pharmacologically increasing the proportion of oxygenated HbS in RBCs may inhibit polymerization, prevent sickling and provide long term disease modification. We report that GBT440, a small molecule which binds to the N‐terminal α chain of Hb, increases HbS affinity for oxygen, delays in vitro HbS polymerization and prevents sickling of RBCs. Moreover, in a murine model of SCD, GBT440 extends the half‐life of RBCs, reduces reticulocyte counts and prevents ex vivo RBC sickling. Importantly, oral dosing of GBT440 in animals demonstrates suitability for once daily dosing in humans and a highly selective partitioning into RBCs, which is a key therapeutic safety attribute. Thus, GBT440 has the potential for clinical use as a disease‐modifying agent in sickle cell patients.     

Hb Oegstgeest [α104(G11)Cys → Ser (α1)]. A New Hemoglobin Variant Associated with a Mild α-Thalassemia Phenotype

A microcytic hypochromic anemic state was observed in an 8-year old Black female of Surinam origin during pre-operative Hb S [β6(A3)Glu → Val] screening. Her high zinc protoporphyrin (ZPP) level suggested a chronic iron depletion but, in contrast, the high red blood cell (RBC) count (5.85 × 10¹²/L) was indicative of a possible coexisting thalassemia. No abnormal hemoglobin (Hb) bands were present on high performance liquid chromatography (HPLC) or alkaline electrophoresis and the Hb A₂ level was normal. Break point polymerase chain reaction (PCR) failed to reveal any of the common α-thalassemia (thal) mutations but selective DNA sequencing of both α-globin genes disclosed a TGC →AGC transversion at codon 104 of the α1 gene. Cystine at codon 104 is involved in α/β globin contact and has been described to be a critical amino acid of the α2 chain when substituted by a tyrosine (Hb Sallanches), inducing Hb H (β₄) disease in the homozygous state. Our heterozygous patient had a moderate anemia of 12.2 g/dL and a borderline haptoglobin suggesting some degree of hemolysis.     

Hb San Cataldo [β144(HC1)Lys→Thr; HBB: C.434A > C]: A New Hemoglobin Variant with Increased Affinity for Oxygen

A 59-year-old Italian woman came to our center for revaluation of a previous diagnosis of polycythemia vera. The patient presented with a lifelong history of polycythemia, no increase in white blood cells (WBCs) and platelets, and a negative bone marrow biopsy. Analysis of hemoglobin (Hb) fractions showed an abnormal fast moving Hb component. We aimed to determine if this variant was the cause of polycythemia in this patient. A complete blood count (CBC) was performed by an automated cell counter and Hb fractions were determined by high performance liquid chromatography (HPLC). Standard stability tests and oxygen affinity evaluation were also performed. Genomic DNA was extracted from peripheral blood leukocytes using the phenol chloroform method and the entire β-globin gene was analyzed by direct sequencing. At the hematological level, no anemia or hemolysis was observed but an abnormal Hb fraction was detected using cation exchange HPLC. Molecular analysis of the β-globin gene showed heterozygosity for an AAG?>?ACG substitution at codon 144, resulting in a Lys→Thr amino acid replacement. We demonstrated that this is a new Hb variant with increased oxygen affinity. Its altered physiology is caused by the reduction of 2,3-diphosphoglycerate (2,3-DPG) effects, due to an amino acid substitution in the central pocket near the C-terminal of the β chain. We called this new variant Hb San Cataldo for the native city of proband.     

Inappropriately low red cell 2,3-diphosphoglycerate and p50 in transfused beta-thalassemia

The relationships among hemoglobin concentration (Hb), red cell 2,3- diphosphoglycerate (2,3-DPG), and p50 were studied in 20 chronically hypertransfused patients with thalassemia major. In the nontransfused control group, which included normal individuals as well as patients with sickle cell disease or iron deficiency anemia, the Hb correlated inversely with both 2,3-DPG concentration and p50, as is well established. In contrast, however, prior to transfusion, at the nadir of Hb, patients with thalassemia major had inappropriately low 2,3-DPG concentrations and p50s. These findings occurred in all patients, regardless of whether they had received packed, leukocyte-poor, or frozen-thawed red cells. The hypothesis that the time of blood storage was a factor was excluded by repeatedly transfusing one patient with packed red cells administered within 4 hr of collection in CPDA-1. A second hypothesis, that red cell function might be impaired by the iron- overloaded thalassemic environment, was excluded by studying a newly diagnosed, newly transfused patient with aplastic anemia. In both cases, the same inability to appropriately increase 2,3-DPG and p50 as the Hb fell during the intertransfusion interval was noticed. These data suggest that red cells of chronically transfused patients are unable to adapt to the decline in Hb that occurs during the intertransfusion interval.     

Comparison of Sickle Cell-β° Thalassaemia with Homozygous Sickle Cell Disease

Clinical and haematological features in 41 patients with sickle cell-beta0 thalassaemia (Sbeta0 thalassemia) and in 123 age--sex matched controls with homozygous sickle cell (SS) disease were compared. Persistence of splenomegaly was more common and fetal loss less common in Sbeta0 thalassemia but other clinical features were similar in the two genotypes. Total haemoglobin, Hb A2, PCV, CCV, and red cell count were significantly higher and MCV, MCH, MCHC, and ISC counts significantly lower in Sbeta0 thalassaemia. Proportional reticulocyte counts were significantly lower in Sbeta0 thalassaemia but there was no difference in absolute reticulocyte counts. Persistence of splenomegaly and low ISC counts are compatible with decreased intravascular sickling which may result from the lower mean cell haemoglobin S concentration in Sbeta0 thalassaemia. If beneficial effects of a low MCHC can be confirmed then a carefully monitored trial of iron deficiency in SS disease may be a logical experimental procedure.     

Inhibition of hemoglobin S polymerization by N-terminal band 3 peptides: New class of inhibitors: Solubility studies

Two synthetic peptides corresponding to the N-terminal amino acids (AA) of band 3 were designed to inhibit deoxyhemoglobin S (deoxy S) polymerization through two different mechanisms. Peptide I, an N:1–15AA fragment, was employed to bind to the 2,3-diphosphoglycerate (2,3-DPG) receptor locus of single deoxy S molecules with 5–7 AA extending internally and the remaining 10-8 AA projecting external to hemoglobin (Hb) S, thereby inhibiting polymerization by steric hindrance. Peptide II consisted of two N:1-8AA + K (lysine) sequences linked by a coupler through the lysine, and it was employed to bind to the 2,3-DPG loci of two deoxy S molecules, tethering them together to form “binary hemoglobin complexes” incapable of entering the polymer chains. Decreased polymerization would result from reduction in effective concentration of deoxy S. Binding of peptides to the 2,3-DPG receptor loci was demonstrated by a progressive rightward shift in the hemoglobin oxygen binding curves as a function of increasing peptide concentrations. Inhibition of deoxy S polymerization was studied by equilibrium solubility measurements of purified, stripped solutions of Hb S. Physiologically significant inhibition was demonstrated for both peptides with near-maximum increases in solubility achieved by Peptide II at 1:1 peptide:Hb S ratios. These peptides represent a new class of inhibitors of deoxy S polymerization. © 1994 Wiley-Liss, Inc.     

Functional characteristics of red cells of sickle cell anemia patients with and without α-thalassemia-2

Oxygen equilibrium curves, red cell indices, 2,3-DPG levels, and the percentages of ISC and Hb F were determined for red cell fractions isolated by Dextran 40 density gradient centrifugation from blood of a sickle cell anemia (SS) patient, an SS patient with an additional homozygosity for α-thalassemia-2, and a normal control. In the SS patient, the MCHC and P₅₀ values increased and 2,3-DPG levels decreased with an increase in red cell density; the P₅₀ values were directly related to the MCHC values and inversely related to the 2,3-DPG levels. The bottom fraction contained about 80% ISC, and had the highest MCHC and P₅₀ values and the lowest 2,3-DPG level. In the SS α-thalassemia-2 patient, a decrease in the P₅₀ value corresponded with a decrease in 2,3-DPG levels because no change in MCHC value was observed. The bottom fraction contained about 10% ISC and had the lowest P₅₀ value. These data confirm that both MCHC and 2,3-DPG levels influence the oxygen affinity of SS red cells; an increase in MCHC decreases the oxygen affinity to a great extent while a concomitant decrease in 2,3-DPG level partially abolishes this effect.     

2,3-Diphosphoglycerate and intracellular pH as interdependent determinants of the physiologic solubility of deoxyhemoglobin S

We have established that 2,3-diphosphoglycerate (2,3-DPG) content and intracellular pH exert separate, but interdependent, effects on the equilibrium solubility (csat) of deoxyhemoglobin S (deoxy-Hb S) that act in concert to modulate intraerythrocytic polymer formation. In a nonphysiologic csat assay system, a steep dependence of csat on pH in the physiologic range 7.0 to 7.6 was shown for both stripped (Hb) and DPG-saturated deoxy-Hb S (Hb-DPG). The solubility-pH profile for Hb under near-physiologic buffer conditions also showed that csat increased steeply in the same pH range (6.8 to 7.6). The effect of 2,3- DPG on csat under near-physiologic conditions was evaluated separately. At pH 7.20, the pH of the human red blood cell, csat values for Hb and Hb-DPG were 19.56 +/- 0.14 and 17.95 +/- 0.45 g/dL, respectively, indicating that the solubility of Hb-DPG is lower than that of Hb by 8.2% +/- 2.3%. Thus, binding of 2,3-DPG in the beta-cleft promotes the polymerization of deoxy-Hb S, the ultimate determinant of cell sickling. Furthermore, because of the abnormal Bohr effect of sickle blood (approximately double that of normal blood), the intracellular pH of deoxygenated sickle erythrocytes should be approximately 0.28 pH unit higher than that of oxygenated cells (ie, 7.41 v 7.13). At the higher pH, the corresponding csat for Hb-DPG is 20.22 g/dL, which is the best estimate of the intrinsic solubility of T-state Hb S under conditions that approximate closely those of pH, temperature, ionic strength, and 2,3-DPG saturation in the fully desaturated sickle erythrocyte.     

Identification of Hb Constant Spring (HBA2: c.427T > C) by an Automated High Performance Liquid Chromatography Method

Abstract

Laboratory investigation of hemoglobinopathies includes complete blood count (CBC), hemoglobin (Hb) typing by high performance liquid chromatography (HPLC) and DNA analysis. DNA analysis is the most reliable method but requires a manually laborious procedure and is time consuming. A more practical method of detecting abnormal Hbs is the HPLC technique, because it is more rapid and easier to interpret. Hb Constant Spring (Hb CS; HBA2: c.427T?>?C) is an abnormal variant that is labile and difficult to detect using conventional methods. To evaluate the efficiency of Hb CS determination by HPLC, blood samples from 578 subjects were analyzed using an automated cell analyzer for hematological parameters, automated HPLC for Hb identification, and polymerase chain reaction (PCR) for α-thalassemia (α-thal) and Hb CS confirmation. These included 169 normal, 119 heterozygous α-thal-2, 30 homozygous α-thal-2, 177 heterozygous α-thal-1, 59 heterozygous Hb CS, seven homozygous Hb CS and 17 compound heterozygous α-thal-2 and Hb CS subjects. The results showed that sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of Hb CS by HPLC were 93.78, 99.80, 98.73 and 99.00%, respectively. The mean of misdiagnosis value of the three groups of Hb CS subjects (total 83) was 6.02% (n?=?5), with percentages for heterozygous Hb CS, homozygous Hb CS, and compound heterozygous α-thal-2 and Hb CS being 6.8, 0.0 and 5.9%, respectively. The HPLC method yielded good results, although it may also lead to misdiagnosis of Hb CS due to the relatively small amount and lability.     

The Clinical and Laboratory Spectrum of Hb C [β6(A3)Glu→Lys,GAG>AAG] Disease

Newborn screening (NBS) provides early diagnosis of sickle hemoglobinopathies. After Hb S [β6(A3)Glu→Val, GAG>GTG], Hb C [β6(A3)Glu→Lys, GAG>AAG] is the most common hemoglobin (Hb) abnormality identified in the United States (1,2). Published data regarding children with Hb C disease are limited. This study was conducted to summarize a single institution’s clinical and laboratory data for patients with Hb C disease, specifically homozygous Hb CC and its variants over a 10-year period. Forty-seven patients, whose mean age at diagnosis was 2.9 years (range 0.04 to 23 years), were identified. Twenty-nine had Hb CC and the remainder had compound heterozygous variants [10 Hb C/β⁺-thalassemia (β⁺-thal), four Hb C/β⁰-thal, and one each with Hb C/Hb Hope or β136(H14)Gly→Asp (GGT>GAT), Hb C/Hb Lepore (a hybrid δβ-globin gene), Hb C/HPFH (hereditary persistence of fetal Hb) [probably a ^Gγ HPFH-2 (the Ghanaian type)], and Hb C/Osu-Christiansborg or β52(D3)Asp→Asn (GAT>AAT)]. All patients had mild microcytic anemia with reticulocytosis and frequent target cells on peripheral smear. Splenomegaly or cholelithiasis occurred in 2.6% of patients <8 years of age, however, these symptoms were more common (71.0%) in patients >8 years of age. No patient had serious infections or painful events resembling vasoocclusion. Accurate diagnosis and understanding of Hb C-related disorders helped to avoid confusion with sickle hemoglobinopathies and aided in proper clinical management.     

Molecular Survey of Hemoglobinopathies in Myanmar Workers in Northeast Thailand Revealed an Unexpectedly High Prevalence of α+-Thalassemia

Abstract

To provide the molecular information on hemoglobinopathies in the Myanmar population, the study was carried out on Myanmar workers in Khon Kaen Province in northeast Thailand. A total of 300 anonymous Myanmar factory workers were randomly recruited during their annual medical checkup. Hemoglobinopathies were identified using hemoglobin (Hb) and DNA analyses. These identified heterozygous α⁰-thalassemia (α⁰-thal) [– –^SEA (Southeast Asian) deletion] (n?=?5, 1.7%), heterozygous α⁺-thal (n?=?103, 34.3%), homozygous α⁺-thal (n?=?12, 4.0%), heterozygous β-thalassemia (β-thal) (n?=?3, 1.0%), heterozygous β-thal with homozygous α⁺-thal (n?=?2, 0.7%), double heterozygous β-thal/α⁰-thal (n?=?1, 0.3%)], heterozygous Hb E (HBB: c.79G>A) with α⁰-thal/α⁺-thal (n?=?1, 0.3%), heterozygous Hb E (n?=?27, 9.0%), heterozygous Hb E with α⁺-thal (n?=?24, 8.0%), homozygous Hb E with α⁰-thal/α⁺-thal (n?=?1, 0.3%), homozygous Hb E (n?=?3, 1.0%) and homozygous Hb E with heterozygous α⁺-thal (n?=?3, 1.0%). No thalassemia defect was found in the remaining 115 subjects (38.4%). Haplotypes associated with Hb E and Hb Dhonburi (or Hb Neapolis) [β126(H4)Val→Gly, codon 126 (T>G), HBB: c.380T>G] are reported. While the proportions of α⁰-thal, β-thal and Hb E are comparable to those described in neighboring countries, a markedly high prevalence of α⁺-thal (48.6% in total) is unexpected. The molecular information obtained should provide necessary information for diagnostic improvement and planning of a prevention and control program of severe thalassemia in the Myanmar population.