Molecular epidemiology and hematological profiles of hemoglobin variants in southern Thailand

Data on hemoglobin (Hb) variants in southern Thailand are lacking. This study aimed to reassess the frequency of Hb variants and the clinical aspects of compound heterozygous Hb variant with other hemoglobinopathies. We enrolled 13,391 participants from ten provinces in southern Thailand during 2015-2022. Hb analysis was performed using capillary electrophoresis, and mutations in the HBA and HBB genes were identified using PCR or DNA sequencing. Hb variants were identified in 337 (2.5%) unrelated subjects. Nine β-chain variants, namely Hb Malay (76.9%), Hb C (10.1%), Hb D-Punjab (2.9%), Hb G-Makassar (2.3%), Hb Dhonburi (2.3%), Hb Tak (1.4%), Hb J-Bangkok (1.4%), Hb New York (0.3%), and Hb Hope (0.3%), and four α-chain variants-Hb G-Georgia (HBA1) (0.9%), Hb G-Georgia (HBA2) (0.3%), Hb Q-Thailand (0.6%), and Hb St. Luke's-Thailand (0.3%)-were identified. The southern population exhibited a distinct spectrum of Hb variants compared to that observed in the populations from other areas. Several compound heterozygous genotypes were also identified. Combining Hb Malay with Hb E or high Hb F determinants did not require a blood transfusion. This study provides essential information for genetic counseling in thalassemia prevention and control programs in this region.

Compound Heterozygosity for Hb D-Ibadan (HBB: c.263C>A) and Hb C (HBB: c.19G>A)

We report an individual with a compound heterozygosity for Hb D-Ibadan (HBB: c.263C>A) and Hb C (HBB: c.19G>A), a hemoglobin (Hb) combination not previously identified. The compound hemoglobinopathy was detected in a young woman during routine prenatal screening. Variant Hbs were identified and confirmed by high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) followed by Sanger DNA sequencing. Hb D-Ibadan was present in significant excess over Hb C (70.3 to 24.4%). A complete blood count (CBC) revealed moderate microcytosis with slight anemia. The history suggests the Hb combination is clinically silent. The findings indicate the compound hemoglobinopathy demonstrates thalassemia minor-like red cell indices with an unequal distribution of the variant Hbs. Comparison with other Hb D-like heterozygous conditions is reviewed.

Spectrum of Types of Thalassemias and Hemoglobinopathies: Study in a Tertiary Level Children Hospital in Bangladesh

Thalassemias and hemoglobinopathies are the most common hemolytic congenital disorders in Bangladesh as in many parts of the world. This study was done to find the common types of thalassemias and abnormal hemoglobin variants seen in Bangladeshi populations. A total of 4813 samples were analyzed for hemoglobin disorders out of which 2308 (49.95%) showed abnormalities. The samples were analyzed by Bio Rad D 10 Analyzer in 3914 (81.32%) cases, BIORAD VARIANTβ thalassemia short program using the principle of high performance liquid chromatography in 474 (9.85%) cases and by CAPILLARYS 2 FLEX PIERCING utilizing capillary electrophoresis in 425 (8.83%) cases. The samples were analyzed in the Department of Biochemistry and Molecular Biology of Dhaka Shishu (Children) Hospital, Dhaka, Bangladesh. The common hemoglobin disorders seen were β trait 863 (17.94%), Hb E trait 601 (12.50%), Hb E β thalassemia 524 (10.87%), β thalassemia major 192 (4.00 %), Hb E disease 99 (2.05%). Other Hb abnormalities detected were Hb D trait 17 (0.35%), Sickle cell trait 4 (0.08%), hereditary persistence of fetal hemoglobin (HPFH) 2 (0.04%), and Hb Lepore, δ β thalassemia, sickle cell β thalassemia, Sickle cell disease, compound heterozygote for HbE+D and Hb Q band one case each (0.02%).

Structural and Functional Characterization of a New Double Variant Haemoglobin (HbG-Philadelphia/Duarte α(2)β(2))

WE REPORT THE FIRST CASE OF COSEGREGATION OF TWO HAEMOGLOBINS (HBS): HbG-Philadelphia [α68(E17)Asn → Lys] and HbDuarte [β62(E6)Ala → Pro]. The proband is a young patient heterozygous also for β°-thalassaemia. We detected exclusively two haemoglobin variants: HbDuarte and HbG-Philadelphia/Duarte. Functional study of the new double variant HbG-Philadelphia/Duarte exhibited an increase in oxygen affinity, with a slight decrease of cooperativity and Bohr effect. This functional behaviour is attributed to β62Ala → Pro instead of α68Asn → Lys substitution. Indeed, HbG-Philadelphia isolated in our laboratory from blood cells donor carrier for this variant is not affected by any functional modification, whereas purified Hb Duarte showed functional properties very similar to the double variant. NMR and MD simulation studies confirmed that the presence of Pro instead of Ala at the β62 position produces displacement of the E helix and modifications of the tertiary structure. The substitution α68(E17)Asn → Lys does not cause significant structural and dynamical modifications of the protein. A possible structure-based rational of substitution effects is suggested.

Hemoglobin D-Punjab syndromes in India: a single center experience on cation-exchange high performance liquid chromatography

BACKGROUND

Hemoglobin-D-Punjab (HbDP) is an uncommon structural hemoglobin variant, which is reported to be prevalent in North Western India. There are only a few small series, family studies and anecdotal reports of this entity in the literature. We report the largest single center experience on this entity diagnosed by cation-exchange high performance liquid chromatography (CE-HPLC) from India.

AIM

To document and analyze the clinical, hematological and chromatographic parameters of patients with HbDP syndromes.

PATIENTS AND METHODS

A total of 6889 blood samples (both pediatric and adult) were screened for hemoglobinopathies and structural hemoglobin variants by CE-HPLC; beta thal short program (BTS), Bio-Rad variant for evaluation of anemia and for family and antenatal screening studies.

RESULTS AND CONCLUSION

A total of 484 cases of structural hemoglobin variants comprising of HbS, E, D-Punjab, D Iran, Lepore, and J-Meerut were detected. HbDP syndromes constituted 38 (7.8%) of all hemoglobin variants and 0.55% of all the samples screened for hemoglobinopathies. Heterozygous HbDP constituted 23 of 38 (61%) cases and homozygous HbD/D, HbS/D and HbD/beta constituted 9/38 (24%), 2/38 (5%), and 4/38 (10%) respectively. HbDP syndromes are not uncommon and are relatively underdiagnosed. CE-HPLC has the advantage of rapid detection and accurate quantitation. Electrophoresis and CE-HPLC can be complementary in making accurate diagnosis of these entities.

A family with multiple mutations and sequence variations in the alpha- and beta-globin gene clusters

BACKGROUND

Usually, laboratory diagnostics of hereditary hemoglobin disorders is fairly straightforward. Sometimes, however, correct diagnosis can be difficult. In this study, we describe a family with multiple mutations and sequence variations in the alpha- and beta-globin gene clusters.

METHODS

Hemocytometry results were obtained using an automated cell counter. Hemoglobin variant analysis was performed by cation-exchange HPLC. PCR and DNA sequence analyses were used to identify mutations in the globin genes.

RESULTS

The proposita was referred to our laboratory for hematological evaluation [hemoglobin 145 g/L (119-155 g/L) mean corpuscular volume 72 fl (80-97 fl), mean corpuscular hemoglobin 26 pg (28-36 pg), erythrocytes 5.6 x 10(12)/L (3.7-5.0 10(12)/L)]. Characterization and quantification of hemoglobin variants showed 11.3% HbA1, 4.4% HbA2, 58.9% HbC and 23.0% HbF. Subsequent analysis revealed, in addition to a heterozygous HbC mutation, the presence of a beta-thalassemia causing mutation (-90C>T), a heterozygous alpha-thalassemia (-alpha(-3.7)/alpha alpha) and three different gamma-globin sequence variations. Additional molecular analysis was performed in all family members.

CONCLUSIONS

In the family presented in this study, 10 different mutations were found in the globin genes. Molecular analysis was necessary to clarify hemoglobin variant analysis, in particular the low amount of HbA1 in the proposita. Knowledge of the molecular background facilitates in the understanding of the hematological parameters and proper counseling of the patient.

Observation of a rare hemoglobin variant [Hb Lulu island, beta107(G9)Gly-->Asp, GGC-->GAC] co-inherited with a beta+-thalassemia mutation [IVS-I-110 (G-->A)] or in the heterozygous state in a Greek-Albanian family

We report clinical, hematological, biochemical, functional and molecular studies carried out on two first cousins from a Greek-Albanian family who have clinical and hematological findings consistent with the diagnosis of thalassemia intermedia. DNA studies determined that they had co-inherited a common Mediterranean beta-thalassemia (thal) mutation, IVS-I-110 (G-->A), in trans to a beta-globin gene mutation at codon 107 (GGC-->GAC), predicted to give rise to a rare unstable beta chain variant Hb Lulu Island or beta107(G9)Gly-->Asp.

Compound heterozygote states for Hb C/Hb Malay and Hb C/Hb E in pregnancy: A molecular and hematological analysis

Hemoglobin (Hb) C (alpha2beta(2)6Glu-Lys) is a variant Hb found mainly in West Africa where individuals carrying both Hb C and Hb S (alpha2beta(2)6Glu-Val) usually have a disease similar to sickle cell disease. The Hb C molecule has reduced solubility leading to crystal formation and hemolytic anemia. We report a hitherto undescribed interaction of Hb C and Hb Malay (alpha2beta(2)19Asn-Ser) in a Thai individual. She was a 24-year-old pregnant woman with moderate anemia who had the following hematologic data; Hb 8.9 g/dl, Hct 30.0%, MCV 81.0 fl, MCH 24.1 pg, MCHC 29.7 g/dl, RDW 17.1% and instead of Hb crystal a marked number of target cell in peripheral blood was observed. Hb analysis revealed 22.5% Hb Malay, 64.6% Hb C and 4.5% Hb A2. Globin gene analyses demonstrated that she carried the betaC mutation (beta6: GAG-AAG) in trans to the betaMalay mutation (beta19: AAC-AGC). Hematologic data of the patient were compared to those of the compound heterozygote for Hb C and Hb E (alpha2beta(2)26Glu-Lys) found in 5 other unrelated Thai pregnant women and 11 pregnant women with Hb C heterozygote with or without co-inheritance of alpha-thalassemia who had much lower Hb C levels and the non-pregnant women with Hb C heterozygote and a compound Hb E/Hb Malay syndrome. Different genotype-phenotype correlations observed in these Thai patients with Hb C disorders are illustrated.

Hb SE disease: a clinico-hematological profile

Hb S and Hb E are globally common hemoglobinopathies. However, Hb SE double heterozygous state is uncommon, with only 25 cases reported so far in literature. We present two more cases. One presented with gallstones, and the other was asymptomatic. This type of disorder was previously described as a relatively asymptomatic condition compared to HbSS. A review of the 25 reported cases in literature shows that 40.7% (11/27) of these cases are symptomatic. Gender, hematological parameters and levels of Hb S, E or F do not predict clinical severity.

Analysis of minor hemoglobins by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

BACKGROUND

Hemoglobin (Hb) heterogeneity arises mainly from posttranslational modifications of the globin chains, and cation-exchange chromatography reveals falsely increased concentrations of some minor Hbs in the presence of abnormal Hbs. Here we describe a method for identification of the globin chains and their posttranslational modifications contained in the Hb fractions.

METHODS

We used cation-exchange HPLC (PolyCAT A column) for separation of Hb fractions and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for analysis of the separated globin chains. Globin chains were identified by their molecular masses. Posttranslational modifications of globin chains were identified by digestion of the proteins with endoproteinase V8 before MALDI-TOF MS of the resulting peptides.

RESULTS

Analysis of the HbA2 fractions of patients with HbS revealed 4 different globin chains. We found, in addition to the expected alpha- and delta-chains, the carbamylated alpha- and the betaS-chains. Additionally, we analyzed HbH, Hb Barts, HbA 1b, pre-HbA 1c, HbA 1c, HbF1, HbF, HbA 1d3a, HbA 1d3b, HbA2, and HbC1 fractions from control and pathologic blood samples. We identified several posttranslational modifications of the globin chains, such as pyruvatization, glycation, acetylation, carbamylation, and acetaldehyde adduct formation.

CONCLUSIONS

The native and posttranslationally modified globin chains in minor and major Hbs are unambiguously identified by MALDI-TOF MS. A minor Hb containing the carbamylated alpha- and the betaS-chain elutes at the same time as normal HbA2 (alpha2delta2) and thus leads to falsely increased HbA2 values in patients with HbS when blood is analyzed with PolyCAT A chromatography.

Molecular characterization of Hb D-Punjab [beta121(GH4)Glu-->Gln] in Thailand

We describe the hematological and DNA characterization of Hb D-Punjab [beta121(GH4)Glu-->Gln] in Thailand. Nine patients from five unrelated families were studied; four patients were simple carriers of Hb D-Punjab, two were compound heterozygotes for Hb D-Punjab/beta+-thalassemia; another two patients were double heterozygotes for Hb D-Punjab and alpha-thalassemia-2, and one patient was a compound heterozygote for Hb D-Punjab and Hb E [beta26(B8)Glu-->Lys]. Typical thalassemic indices with hypochromic microcytosis were observed in compound Hb D-Punjab/ beta+-thalassemia and Hb D-Punjab/Hb E but normal hematological profiles were observed in the remaining cases. DNA sequencing of the beta-globin gene identified the GAA-->CAA substitution at codon 121 causing Hb D-Punjab in all cases, and the -28 (A-->G) mutation for the beta+-thalassemia alleles. beta-Globin gene haplotype analysis demonstrated, for the first time, that all these Asian beta(D-Punjab) globin genes were associated with haplotype [-++-+++], previously undescribed in other populations. The finding of Hb D-Punjab in Thailand is compatible either with an independent origin of this abnormal hemoglobin or a spread of the Hb D-Punjab gene with a single origin among Asians.

Molecular characterization of hemoglobin C in Thailand

We describe hematologic and DNA characterization of 12 hemoglobin C heterozygotes and three compound heterozygotes for hemoglobin C and hemoglobin E found in Thailand. Amplification and DNA analysis of genomic DNA by the polymerase chain reaction procedure permitted the identification of the beta(C) mutation at codon 6 of beta-globin gene (beta 6; GAG-AAG). beta-Globin gene haplotype analysis demonstrated that all beta(C) globin genes detected in these Thai individuals were associated with the haplotype (+ - - - - - +), indicating a non-African origin of this abnormal hemoglobin in Thailand. On routine hemoglobin typing, hemoglobin C is usually mistakenly identified as hemoglobin E because of theirs similar mobilities on cellulose acetate electrophoresis. The simple DNA assay for hemoglobin C based on an allele-specific polymerase chain reaction for accurate diagnosis of hemoglobin C was therefore developed.

Laboratory Investigation of Hemoglobinopathies and Thalassemias: Review and Update

Structural hemoglobin (Hb) variants typically are based on a point mutation in a globin gene that produce a single amino acid substitution in a globin chain. Although most are of limited clinical significance, a few important subtypes have been identified with some frequency. Homozygous Hb C and Hb S (sickle cell disease) produce significant clinical manifestations, whereas Hb E and Hb D homozygotes may be mildly symptomatic. Although heterozygotes for these variants are typically asymptomatic, diagnosis may be important for genetic counseling. Thalassemia, in contrast, results from quantitative reductions in globin chain synthesis. Those with diminished β-globin chains are termed β-thalassemias, whereas those with decreased α-chain production are called α-thalassemias. Severity of clinical manifestations in these disorders relates to the amount of globin chain produced and the stability of residual chains present in excess. The thalassemia minor syndromes are characterized clinically by mild anemia with persistent microcytosis. Thalassemia intermedia (i.e., Hb H disease) is typified by a moderate, variably compensated hemolytic anemia that may present with clinical symptoms during a period of physiologic stress such as infection, pregnancy, or surgery. The thalassemia major syndromes produce severe, life-threatening anemia. α-Thalassemia major usually is incompatible with extrauterine life; β-thalassemia major presents in infancy and requires life-long transfusion therapy and/or bone marrow transplantation for successful control of the disease. Double heterozygosity for certain structural variants and/or thalassemia syndromes may also lead to severe clinical disease. Several guidelines have been published that outline the required steps for hemoglobinopathy and thalassemia investigation. The availability of HPLC has streamlined many of these requirements, allowing an efficient stepwise diagnostic strategy for these complex disorders.

Jamaican Sbeta+-thalassaemia: mutations and haematology

The sickling disorders are a common cause of morbidity and mortality in Jamaica. Sickle cell beta+-thalassaemia is the fourth commonest form, occurring in one in every 3000 births. This is a heterogeneous condition, producing HbS, HbF and HbA2 with variable amounts of HbA, depending on the mutation and, within a defined population, only a few beta-thalassaemia mutations occur at high frequency. This study establishes the frequency of beta-thalassaemia mutations in Sbeta+-thalassaemia patients in Jamaica. In addition, comparison of the haematological phenotypes is possible by looking at the 'average steady-state haematology' of the different mutational groups. Blood samples from 132 unrelated Sbeta+-thalassaemia patients attending the MRC Sickle Cell Unit at the University of the West Indies were analysed by amplification refractory mutation system (ARMS) polymerase chain reaction (PCR) or sequencing to determine the nature and frequencies of the underlying beta-thalassaemia mutations. Ten mutations were identified, four of which accounted for 93% of patients studied. These were -29(A --> G) in 71 (54%), -88(C --> T) in 27 (20%), polyA(T --> C) in 17 (13%) and IVS1-5(G --> C) in nine (7%). The six remaining mutations found at low frequency were C24(T --> A) in two patients and one each of IVS2-848(C --> A), -90(C --> T), IVS1-5(G --> T), IVS1-5(G --> A) and IVS1-6 (T --> C). In one individual, no mutation was found. The three commonest mutations were all associated with haemoglobin levels of greater than 10 g/dl, whereas IVS1-5 (G --> C) had a more severe haematological phenotype. The predominance of -29(A --> G) and -88(C --> T) is in keeping with other studies on populations of African origin. IVS1-5(G --> C) is found chiefly in Indian populations, and all affected families acknowledged Indian ancestry, reflecting the prominent Indian community in Jamaica.