Hemoglobin Constant Spring among Southeast Asian Populations: Haplotypic Heterogeneities and Phylogenetic Analysis

Uncommon Combination of Hemoglobin Jax and Hemoglobin Constant Spring Leading to Microcytic Anemia

BACKGROUND Thalassemia and hemoglobin (Hb) variants are the most common hereditary red blood cell disorders worldwide. Alpha-thalassemia and alpha-globin variants are caused by mutations of the alpha-globin genes (HBA2 and HBA1), resulting in impaired alpha-globin production and structurally abnormal globin, respectively. Clinical severity of alpha-thalassemia correlates with the number of affected alpha-globin genes, yielding a spectrum of clinical manifestations from mild to severe anemia. Routine diagnosis involves Hb analysis and PCR-based methods, yet identifying rare variants necessitates comprehensive clinical and hematologic laboratory data. The knowledge of phenotype and genotype correlation is useful for genetic counseling and treatment planning. CASE REPORT A 59-year-old Thai woman presented with chronic anemia. Her baseline Hb level ranged between 8.0 and 9.0 g/dL, with no history of transfusion. Physical examination showed mild pallor, without enlarged liver and spleen. Laboratory investigations showed microcytic, hypochromic anemia and abnormal Hb peak by Hb analysis (retention time 4.58 min by HPLC method). Common alpha-globin gene deletions, including the Southeast-Asian/Thai 3.7 kb and 4.2 kb deletions were tested using gap-PCR, with none of these deletions detected. Direct DNA sequencing revealed a compound heterozygosity of Hb Jax (HBA2: c.44G>C) and Hb Constant Spring (HBA2: c.427T>C). CONCLUSIONS Compound heterozygosity of Hb Jax and Hb Constant Spring results in microcytic anemia. Hb Jax can be identified by Hb analysis, and diagnosis can be confirmed by direct DNA sequencing method. Coinheritance of Hb Jax and alpha-globin variants should be considered in cases with microcytic anemia and a specific Hb peak seen in Hb chromatogram.

Hematological Profile of Hb Adana Among High School Students in Northeast Peninsular Malaysia

Background Hb Adana is a non-deletional alpha (α)-thalassaemia variant resulting from mutations in α1- or α2-globin codon 59 (αCD59), leading to the production of unstable α-globin. Clinical manifestations can vary from silent carrier status to dependence on blood transfusions, hepatosplenomegaly, skeletal deformities, and spinal cord compression. Despite the significance of Hb Adana inheritance, studying this variant poses challenges due to the scarcity of molecular tests and the potential for routine diagnoses to be overlooked. This study aims to investigate the prevalence of Hb Adana among local high school students and assess the hematological parameters and hemoglobin analysis of Hb Adana in Malaysia. Methodology This retrospective study analyzed 13,721 blood samples collected from high school students participating in Malaysia's National Thalassaemia Screening Program at Hospital Raja Perempuan Zainab II (HRPZ II). Deletional α-thalassaemia was detected using multiplex gap-polymerase chain reaction (PCR), while common non-deletional α-thalassaemia was identified using multiplex amplification refractory mutation system (ARMS) PCR. Data were extracted from the HRPZ II database for analysis. Results Among the participants, 2327 individuals were found to have either common deletional (n=1037, 44.6%) or non-deletional (n=1290, 55.4%) α-thalassaemia. Hb Constant Spring was the most prevalent non-deletional α-thalassaemia, accounting for 53.03% of cases. Thirty-one participants (1.33%) exhibited αCD59α/αα, and one (0.04%) had αCD59α/-α3.7. Among the 32 subjects with Hb Adana, 87.5% were Malay, and 12.5% were Orang Asli. Additionally, seven cases of HbE/Hb Adana co-inheritance were identified. Hemoglobin levels in heterozygous Hb Adana individuals ranged from mild anemia to normal, between 95 g/L and 153 g/L. Mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) were approximately 73 fL and 23 pg, respectively. Conclusion This study delineates the distribution of α-thalassaemia mutation patterns among high school students in Kelantan, Northeast Peninsular Malaysia. Our findings indicate that Hb Adana is rare in our region and co-inheritance with an α-gene deletion results in α+-thalassaemia and with HbE, α0-thalassaemia. All heterozygous Hb Adana individuals exhibited low MCVs and MCHs.

Novel secretory organelles of parasite origin - at the center of host-parasite interaction

Reorganization of cell organelle-deprived host red blood cells by the apicomplexan malaria parasite Plasmodium falciparum enables their cytoadherence to endothelial cells that line the microvasculature. This increases the time red blood cells infected with mature developmental stages remain within selected organs such as the brain to avoid the spleen passage, which can lead to severe complications and cumulate in patient death. The Maurer's clefts are a novel secretory organelle of parasite origin established by the parasite in the cytoplasm of the host red blood cell in order to facilitate the establishment of cytoadherence by conducting the trafficking of immunovariant adhesins to the host cell surface. Another important function of the organelle is the sorting of other proteins the parasite traffics into its host cell. Although the organelle is of high importance for the pathology of malaria, additional putative functions, structure, and genesis remain shrouded in mystery more than a century after its discovery. In this review, we highlight our current knowledge about the Maurer's clefts and other novel secretory organelles established within the host cell cytoplasm by human-pathogenic malaria parasites and other parasites that reside within human red blood cells.

Thalassaemia in China

Because of successful thalassaemia prevention programmes in resource-rich countries and it's huge population China now has the greatest number of new cases of thalassaemia globally as well as more people with thalassaemia than any other country. 30 million Chinese have thalassaemia-associated mutations and about 300,000 have thalassaemia major or intermedia requiring medical intervention. Over the past 2 decades there has been tremendous economic growth in China including per capita spending on health care. There is now nation-wide availability and partial or full insurance for prenatal genetic testing, RBC-transfusions, iron-chelating drugs and haematopoietic cell transplants. Prenatal screening and educational programmes have reduced the incidence of new cases. However, substantial challenges remain. For example, regional differences in access to medical care and unequal economic development require innovations to reduce the medical, financial and psychological burdens of Chinese with thalassaemia and their families. In this review we discuss success in preventing and treating thalassaemia in China highlighting remaining challenges. Our discussion has important implications for resource-poor geospaces challenged with preventing and treating thalassaemia.

Direct PCR assays without DNA extraction for rapid detection of hemoglobin Constant Spring and Pakse' genes: application for carrier screening and prenatal diagnosis

Hemoglobin Constant Spring (Hb CS) and Hb Pakse' (PS) are the common non-deletional α⁺-thalassemia found in Thailand. These two variants can cause severe thalassemia syndromes, especially in fetus and neonate. Molecular diagnosis is the only confirmatory method because Hb CS and Hb PS are usually missed by routine screening and Hb analysis. Therefore, we aimed to develop rapid direct PCR for the diagnosis of Hb CS and PS genes. Multiplex direct PCR assays for identifying the Hb CS and PS genes in whole blood (WB) and amniotic fluid (AF) specimens were developed. The assays were firstly validated on 290 unrelated whole blood specimens. Hb CS and PS carriers were identified in 67 (23.1%) and 6 (2.1%) cases, respectively. A 100% concordant result as compared to routine PCR assay was observed. The direct PCR assays have been applied successfully for prenatal diagnosis in two families. The result showed that the fetuses were affected by homozygous Hb CS and compound heterozygous Hb CS/Hb PS. Accurate prenatal diagnosis of these families was observed using the newly developed assays. These assays should be applicable in routine thalassemia diagnostics as well as in the large-scale screening of Hb CS and PS in the region.

Molecular spectrum of Hb H disease and characterization of rare deletional α-thalassemia found in Thailand

Hb H diseases with the clinical features of thalassemia are found in many parts of the world, including Southeast Asia and southern China. There are limitations in molecular data from the population of Thailand, which includes multiple ethnic groups. Here, we characterized the molecular basis of the disease among a large cohort from this region. A total of 479 unrelated Thai patients with Hb H disease were studied. Mutations of the α-globin gene were characterized by conventional gap-PCR and rare genotypes were identified by MLPA analysis and direct DNA sequencing. The molecular characterization showed five common Hb H genotypes (472/479; 98.54%), including three deletional types (-^SEA/-α^3.7; n = 312), (-^SEA/-α^4.2; n = 26), (-^THAI/-α^3.7; n = 1) and two non-deletional types (-^SEA/α^CSα; n = 131), (-^SEA/α^Pakséα; n = 2). Herein, we firstly report a rare genotype of Hb H disease with (-^SA/-α^3.7; n = 1) that has not been documented in Thailand, and rare genotypes related to (-^SEA/-α^16.6; n = 1), and (-^SEA/α^QSα; n = 3) as well. The remaining two cases could not be characterized. The hematological parameters demonstrated that the clinical phenotype of non-deletional Hb H diseases is more severe than the deletional type of α⁺-thalassemia. The molecular spectrum of α-thalassemia is useful for prevention and thalassemia control and genetic counseling for couples at risk in this region.

Presentation of Compound Heterozygous Hemoglobin Constant Spring and Hemoglobin Pakse in Neonates

BACKGROUND

Mutations causing α thalassemia are divided into deletion and nondeletion groups. In the nondeletion group, hemoglobin constant spring (Hb CS) and hemoglobin Pakse (Hb Pakse) are both caused by a termination codon mutation leading to elongation of the α2 globin gene. In the case of Hb CS, the mutation is TAA→CAA, whereas the mutation causing Hb Pakse is TAA→TAT. Clinical hematologic phenotypes are not significantly different. It is important to identify compound heterozygotes for purposes of genetic counseling.

METHODS

We report 5 neonates with compound heterozygous Hb CS/Hb Pakse mutations with respect to clinical courses, hematologic profiles, and management.

RESULTS

Among 5 cases (3 male babies and 2 female babies) with mean birth weight 2982 g (range, 2660 to 3440 g), 3 were diagnosed as compound heterozygous Hb CS/Hb Pakse, 1 as homozygous Hb E with compound heterozygous Hb CS/Hb Pakse, and 1 as heterozygous Hb E with compound heterozygous Hb CS/Hb Pakse. Clinical manifestations included fetal anemia (1 case), neonatal hyperbilirubinemia (5), neonatal anemia (2), hepatosplenomegaly (1), and cholestatic jaundice (1). Three cases required a single phototherapy; 2 cases needed double phototherapy for treatment of severe hyperbilirubinemia. During the first few months of life, all cases had mild anemia, slightly low mean corpuscular volume, wide red cell distribution width, and low red cell counts. At 1 to 3 years of age, all patients still had mild microcytic hypochromic anemia with Hb levels around 10 g/dL, increased reticulocyte count, and wide red cell distribution width.

CONCLUSIONS

Misdiagnosis of Hb Pakse could occur via Hb typing using Hb electrophoresis, because the band comigrates with that of Hb CS. DNA study is the definitive method for diagnosis.

Prenatal diagnosis and management of homozygous hemoglobin constant spring disease

OBJECTIVE

To describe fetal management of homozygous hemoglobin constant spring (Hb CS).

METHODS

Six fetuses with homozygous Hb CS disease undergoing intrauterine transfusion (IUT) were comprehensively reviewed. Additionally, when combined with 8 cases previously reported, a total of 14 cases were analyzed.

RESULTS

The first clues of diagnosis were hydropic changes suggesting fetal anemia. Increased cardiothoracic diameter ratio (CTR) was the most sensitive sonographic marker but slowly changed after IUT, whereas MCA-PSV was the most sensitive in response to IUT. Pre-IUT Hb varied from 1.1% to 6.8%. Gestational age at diagnosis was 17-29 (22.8 ± 3.3) weeks. Rates of adverse obstetric outcomes were relatively high; preterm birth: 35.7%, low birthweight: 42.9%, and fetal growth restriction: 28.6%. All showed good response to IUT with disappearance of hydropic signs and all survived without short-term complications. Their anemia gradually improved in childhood and transfusion independent.

CONCLUSION

Homozygous Hb CS can cause severe fetal anemia. Early diagnosis and IUT can improve neonatal outcomes, probably preventing adult diseases caused by fetal programming.

Molecular characteristics of α+-thalassemia (3.7 kb deletion) in Southeast Asia: Molecular subtypes, haplotypic heterogeneity, multiple founder effects and laboratory diagnostics

OBJECTIVE

The 3.7 kb deletion (-α^3.7) is the most common form of α⁺-thalassemia found in multiple populations which can be classified into three subtypes. In order not to mis-identify it, the molecular information within each population is required. We have addressed this in northeast Thai and Laos populations.

METHODS

Screening for α⁺-thalassemia was initially done on 1192 adult Thai subjects. In addition, 77 chromosomes of Thai newborns and 26 chromosomes of Laos with -α^3.7 α⁺-thalassemia were also examined. All subjects were screened for -α^3.7 α⁺-thalassemia and subtyped by PCR-RFLP assay. Exact deletion breakpoint of each -α^3.7 subtype was determined by DNA sequencing. α-Globin gene haplotypes were determined.

RESULTS

The proportions of -α^3.7 subtypes found in 216 Thai -α^3.7 chromosomes were 94.9% for -α^3.7I, 4.2% for α^3.7II and 0.9% for -α^3.7III. All 26 Laos -α^3.7 chromosomes were of -α^3.7I variety. At least six α-globin gene haplotypes were associated with the -α^3.7I α⁺-thalassemia.

CONCLUSION

All -α^3.7 subtypes were observed among Southeast Asian population. Haplotype analysis indicated a multiple origin of this common disorder in the region. A multiplex PCR assay has been developed for simultaneous detection of all subtypes of -α^3.7 α⁺-thalassemia as well as other α⁺-thalassemia found in the region including -α^4.2 α⁺-thalassemia, Hb Constant Spring and Hb Paksé.

Clinical Course of Homozygous Hemoglobin Constant Spring in Pediatric Patients

BACKGROUND

Hemoglobin (Hb) Constant Spring is an alpha-globin gene variant due to a mutation of the stop codon resulting in the elongation of the encoded polypeptide from 141 to 172 amino acid residues. Patients with homozygous Hb Constant Spring are usually mildly anemic.

METHODS

We retrospectively describe clinical manifestations, diagnosis, laboratory investigations, treatment, and associated findings in pediatric patients with homozygous Hb Constant Spring followed-up at Srinagarind Hospital.

RESULTS

Sixteen pediatric cases (5 males and 11 females) were diagnosed in utero (N=6) or postnatal (n=10). Eleven cases were diagnosed with homozygous Hb Constant Spring, 4 with homozygous Hb Constant Spring with heterozygous Hb E, and 1 with homozygous Hb Constant Spring with homozygous Hb E. Three cases were delivered preterm. Six patients had low birth weights. Clinical manifestations included fetal anemia in 6 cases, hepatomegaly in 1 case, hepatosplenomegaly in 2 cases, splenomegaly in 1 case. Twelve cases exhibited early neonatal jaundice, 9 of which required phototherapy. Six cases received red cell transfusions; 1 (3), >1 (3). After the first few months of life, almost all patients had mild microcytic hypochromic anemia and an increased reticulocyte count with a wide red cell distribution (RDW), but no longer required red cell transfusion. At 1 to 2 years of age, some patients still had mild microcytic hypochromic anemia and some had normocytic hypochromic anemia with Hb around 10 g/dL, increased reticulocyte count and wide RDW. Associated findings included hypothyroidism (2), congenital heart diseases (4), genitourinary abnormalities (3), gastrointestinal abnormalities (2), and developmental delay (1).

SUMMARY

Pediatric patients with homozygous Hb Constant Spring developed severe anemia in utero and up to the age of 2 to 3 months postnatal, requiring blood transfusions. Subsequently, their anemia was mild with no evidence of hepatosplenomegaly. Their Hb level was above 9 g/dL with hypochromic microcytic blood pictures as well as wide RDW. Blood transfusions have not been necessary since then.

Fetal Anemia Causing Hydrops Fetalis From an Alpha-Globin Variant: Homozygous Hemoglobin Constant Spring

BACKGROUND

Fetal anemia is often assumed to be due to red cell alloimmunization and Parvovirus infection, and can lead to hydrops fetalis and death in utero. Other causes, such as mutations of hemoglobin alpha, are less commonly considered.

METHODS

We report 7 cases with fetal anemia causing hydrops fetalis. Serial Doppler ultrasound for measurement peak systolic velocity (PSV) of middle cerebral artery (MCA) was used for evaluation of fetal anemia. Fetal anemia is suggested if the MCA/PSV ratio is >1.5 multiple of median. Cordocentesis was performed subsequently to find the cause of fetal anemia and check fetal hemoglobin for consideration of intrauterine infusion. Investigations for fetal anemia include complete blood count, blood morphology, and blood group of mother and fetus, reticulocyte counts, red cell indices, screening for thalassemia, hemoglobin typing, acid elution test, parvovirus B 19 serology, and TORCH titer (toxoplasmosis, rubella, cytomegalovirus, herpes simplex virus, human immunodeficiency virus, and syphilis). Intrauterine infusion, using irradiated prestorage filtered red cell with hematocrit level of 80%, is indicated if fetal hemoglobin is <10 g/dL.

RESULT

Seven cases with fetal anemia were prenatally diagnosed from gestational ages 20 to 34 weeks. Initial hematocrit in these cases varied from 9% to 17.2%. In each case, causes of anemia were determined using the investigations listed above. All cases underwent uneventfully up to 3 intrauterine transfusions. DNA study for thalassemia demonstrated homozygous Constant Spring (CS) in 5 cases, homozygous CS with heterozygous E in 1 case, and compound heterozygous CS and Pakse in 1 case. The perinatal outcomes were normal term in 5 cases, preterm in 2 cases. Low birth weight was determined in 2 cases. The screening for thalassemia major, including the osmotic fragility and dichlorophenol indophenol precipitation test (DCIP), is not helpful for detecting hemoglobin variants such as Constant Spring or Pakse.

SUMMARY

This study emphasizes homozygous Constant Spring and compound heterozygous CS and Pakse as a cause of hydrops fetalis. Proper management for the fetus after diagnosis can lead to a good fetal outcome. Prevention control programs should include screening of parents for the heterozygous state.

Thalassemia and hemoglobinopathies in an ethnic minority group in Central Vietnam: implications to health burden and relationship between two ethnic minority groups

Thalassemia is a genetic condition that can result in long and expensive treatments, and severe thalassemia may lead to death if left untreated. Couples contributing two genes for thalassemia place their children at particular risk for severe thalassemia. Gene frequency of thalassemia varies in Vietnam, but presents remarkably high levels among some ethnic minority groups. Limited information about thalassemia frequency makes prevention and control of thalassemia difficult. This study aimed to determine gene frequency of certain types of thalassemia among 390 women of reproductive age of the Ta-Oi ethnic minority. Hemoglobin and DNA analyses were carried out to diagnose thalassemia and hemoglobinopathies. Of the total participants, 56.1% (95% CI = 51.1-61.1) carried thalassemia genes. A remarkably high frequency of hemoglobin Constant Spring (Hb CS) of 23.8% (95% CI = 19.7-28.4) was noted. The frequency of α⁺-thalassemia (-3.7 kb deletion) was 26.4% (95% CI = 22.1-31.1), while hemoglobin E (Hb E) and hemoglobin Paksé (Hb Ps) were identified at frequencies of 14.6 (95% CI = 11.2-18.5) and 2.6% (95% CI = 1.4-5.0), respectively. Further analysis of α-globin gene haplotype revealed the same Hb CS haplotype (+ - M + + -) as of the Co-Tu minority, a neighboring minority of the Ta-Oi, indicating that these two minorities may share the same ancestors. This information will be helpful for further studies in population genetics, as well as the development prevention and control program in the region.

Genetic origin of α0-thalassemia (SEA deletion) in Southeast Asian populations and application to accurate prenatal diagnosis of Hb Bart's hydrops fetalis syndrome

α⁰-thalassemia of SEA deletion (—^SEA) is common among Southeast Asian and Chinese. Using haplotype and phylogenetic analyses, we examined the origin of this defect in Southeast Asian populations. Study was done on both normal and α⁰-thalassemia alleles in 3 ethnic groups including 96 Thai, 52 Laotian and 21 Cambodian. Five SNPs encompassing the (—^SEA) including (rs3760053 T>G), (rs1211375 A>C), (rs3918352 A>G), (rs1203974 A>G) and (rs11248914 C>T) were examined using high-resolution melting assays. It was found that 94.0% of Thai, 100% of Laotian and 100% of Cambodian α⁰-thalassemia alleles were linked to the same haplotype: the haplotype H4 (AAGC), representing an Asian specific origin. An G allele of the (rs3760053) was found to be in strong linkage disequilibrium with the α⁰-thalassemia allele in these populations. A multiplex PCR assay was developed to detect simultaneously the (—^SEA) allele and genotyping of a linked (rs3760053) to improve accuracy of prenatal diagnosis of α⁰-thalassemia. Application of this multiplex PCR assay for routine prenatal diagnosis of α⁰-thalassemia in 12 families revealed a 100% concordant result with conventional gap-PCR assay. Therefore, a single genetic origin is responsible for the spread and high prevalence of the (—^SEA) in the region. The multiplex PCR assay developed should provide a double-check PCR system for more accurate diagnosis and allow the monitoring of possible maternal contamination at prenatal diagnosis of this important genetic disorder.