Clinical, hematologic and molecular variability of sickle cell-β thalassemia in western India

Clinical, laboratory, and molecular characteristics of a cohort of children with hemoglobinopathy S/beta-thalassemia

INTRODUCTION

Hemoglobinopathy Sβ-thalassemia (HbSβ-thal) has a wide range of clinical and laboratory severity. There is limited information on the natural history of HbSβ-thal and its modulating factors. We described the molecular, hematological, and clinical characteristics of a cohort of children with HbSβ-thal and estimated its incidence in Minas Gerais, Brazil.

METHODS

Laboratory and clinical data were retrieved from medical records. Molecular analysis was performed by HBB gene sequencing, PCR-RFLP, gap-PCR, and MLPA.

RESULTS

Eighty-nine children were included in the study. Fourteen alleles of β-thal mutations were identified. The incidence of HbSβ-thal in the state was 1 per 22,250 newborns. The most common βS-haplotypes were CAR and Benin. The most frequent βthal-haplotypes were V, II, and I. Coexistence of 3.7 kb HBA1/HBA2 deletion was present in 21.3 % of children. β-thalassemia mutations were associated with several clinical and laboratory features. In general, the incidence of clinical events per 100 patient-years was similar for children with HbSβ0-thal, IVS-I-5 G>A, and IVS-I-110 G>A. Children with HbSβ+-intermediate phenotypes had a more severe laboratory and clinical profile when compared with those with HbSβ+-mild ones. βS-haplotypes and α-thalassemia did not meaningfully influence the phenotype of children with HbSβ-thal.

CONCLUSION

The early identification of β-thalassemia alleles may help the clinical management of these children.

Multiparametric Cardiac Magnetic Resonance Assessment in Sickle Beta Thalassemia

Cardiac involvement in sickle beta thalassemia (Sβ-thal) patients has been poorly investigated. We aimed to evaluate cardiac function and myocardial iron overload by cardiovascular magnetic resonance (CMR) in patients with Sβ-thal. One-hundred and eleven Sβ-thal patients consecutively enrolled in the Myocardial Iron Overload in Thalassemia (MIOT) network were studied and compared with 46 sickle cell anemia (SCA) patients and with 111 gender- and age- matched healthy volunteers. Cine images were acquired to quantify biventricular function. Myocardial iron overload (MIO) was assessed by the T2* technique, while macroscopic myocardial fibrosis was evaluated by the late gadolinium enhancement (LGE) technique. In Sβ-thal and SCA patients, the morphological and functional CMR parameters were not significantly different, except for the left atrial area and left ventricular (LV) stroke volume, indexed by body surface area (p = 0.023 and p = 0.048, respectively), which were significantly higher in SCA patients. No significant differences between the two groups were found in terms of myocardial iron overload and macroscopic myocardial fibrosis. When compared to healthy subjects, Sβ-thal patients showed significantly higher bi-atrial and biventricular parameters, except for LV ejection fraction, which was significantly lower. The CMR analysis confirmed that Sβ-thal and SCA patients are phenotypically similar. Since Sβ-thal patients showed markedly different morphological and functional indices from healthy subjects, it would be useful to identify Sβ-thal/SCA-specific bi-atrial and biventricular reference values.

Role of hydroxyurea therapy in the prevention of organ damage in sickle cell disease: a systematic review and meta-analysis

BACKGROUND

Hydroxyurea is an affordable drug that reduces vaso-occlusive crises and transfusion requirements in sickle cell disease. However, its effectiveness in preventing chronic organ damage is still unclear. This systematic review and meta-analysis aimed to evaluate the role of hydroxyurea in preventing organ morbidity.

METHOD

We included original articles published in English from 1st January 1990 to 31st January 2023, reporting hydroxyurea therapy and organ damage from PubMed, Google Scholar, Scopus, and CrossRef databases. A total of 45 studies with 4681 sickle cell disease patients were evaluated for organ damage.

RESULTS

Our analysis showed that hydroxyurea intervention significantly lowered transcranial Doppler and tricuspid regurgitant velocity, with a standardized mean difference of - 1.03 (- 1.49; - 0.58); I 2 = 96% and - 1.37 (CI - 2.31, - 0.42); I 2 = 94%, respectively. Moreover, the pooled estimate for albuminuria showed a beneficial effect post-hydroxyurea therapy by reducing the risk of albuminuria by 58% (risk ratio of 0.42 (0.28; 0.63); I 2 = 28%).

CONCLUSION

Our study found that a hydroxyurea dose above 20 mg/kg/day with a mean rise in HbF by 18.46% post-hydroxyurea therapy had a beneficial role in reducing transcranial doppler velocity, tricuspid regurgitant velocity, albuminuria, and splenic abnormality.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42023401187.

Genetic Variation and Sickle Cell Disease Severity: A Systematic Review and Meta-Analysis

Importance

Sickle cell disease (SCD) is a monogenic disorder, yet clinical outcomes are influenced by additional genetic factors. Despite decades of research, the genetics of SCD remain poorly understood.

Objective

To assess all reported genetic modifiers of SCD, evaluate the design of associated studies, and provide guidelines for future analyses according to modern genetic study recommendations.

Data Sources

PubMed, Web of Science, and Scopus were searched through May 16, 2023, identifying 5290 publications.

Study Selection

At least 2 reviewers identified 571 original, peer-reviewed English-language publications reporting genetic modifiers of human SCD phenotypes, wherein the outcome was not treatment response, and the comparison was not between SCD subtypes or including healthy controls.

Data Extraction and Synthesis

Data relevant to all genetic modifiers of SCD were extracted, evaluated, and presented following STREGA and PRISMA guidelines. Weighted z score meta-analyses and pathway analyses were conducted.

Main Outcomes and Measures

Outcomes were aggregated into 25 categories, grouped as acute complications, chronic conditions, hematologic parameters or biomarkers, and general or mixed measures of SCD severity.

Results

The 571 included studies reported on 29 670 unique individuals (50% ≤ 18 years of age) from 43 countries. Of the 17 757 extracted results (4890 significant) in 1552 genes, 3675 results met the study criteria for meta-analysis: reported phenotype and genotype, association size and direction, variability measure, sample size, and statistical test. Only 173 results for 62 associations could be cross-study combined. The remaining associations could not be aggregated because they were only reported once or methods (eg, study design, reporting practice) and genotype or phenotype definitions were insufficiently harmonized. Gene variants regulating fetal hemoglobin and α-thalassemia (important markers for SCD severity) were frequently identified: 19 single-nucleotide variants in BCL11A, HBS1L-MYB, and HBG2 were significantly associated with fetal hemoglobin (absolute value of Z = 4.00 to 20.66; P = 8.63 × 10-95 to 6.19 × 10-5), and α-thalassemia deletions were significantly associated with increased hemoglobin level and reduced risk of albuminuria, abnormal transcranial Doppler velocity, and stroke (absolute value of Z = 3.43 to 5.16; P = 2.42 × 10-7 to 6.00 × 10-4). However, other associations remain unconfirmed. Pathway analyses of significant genes highlighted the importance of cellular adhesion, inflammation, oxidative and toxic stress, and blood vessel regulation in SCD (23 of the top 25 Gene Ontology pathways involve these processes) and suggested future research areas.

Conclusions and Relevance

The findings of this comprehensive systematic review and meta-analysis of all published genetic modifiers of SCD indicated that implementation of standardized phenotypes, statistical methods, and reporting practices should accelerate discovery and validation of genetic modifiers and development of clinically actionable genetic profiles.

Compound Heterozygote of Hb S (HBB: c.20A>T)/Hb Westdale (HBB: c.380_396delTGCAGGCTGCCTATCAG): Report of Four Cases from Odisha State, India

We report four cases of compound heterozygotes for Hb S (HBB: c.20A>T) and a rare β⁰-thalassemia (β⁰-thal) mutation, Hb Westdale (HBB: c.380_396delTGCAGGCTGCCTATCAG), characterized by a 17 bp deletion between codons 126 to 131 in exon 3 of the β-globin gene of human hemoglobin (Hb) confirmed by direct β-globin gene sequencing. All four cases were from four unrelated families belonging to the Agharia caste, an endogamous ethnic community of the Sundargarh and Jharsuguda districts of Odisha State, India. Detailed observations indicated that all four cases of Hb S/Hb Westdale were clinically severe. On family screening, six family members were found to be heterozygous for Hb Westdale and were asymptomatic. Deletional α-thalassemia (α-thal) and XmnI polymorphism were studied for all the Hb Westdale cases. The Hb S/Hb Westdale cases had an early median age at onset of symptoms and presentation, more requirement of blood transfusions, splenomegaly and hepatomegaly and were found to be clinically more severe when compared with the Hb S-β-thal with IVS-I-5 (G>C) (HBB: c.92 + 5G>C) cases. Overall, the findings indicate that this rare and hitherto unreported compound heterozygosity of Hb S/Hb Westdale is a clinically significant hemoglobinopathy and its finding in a large endogamous community of Odisha State, India will have important implication in the epidemiology and understanding of the clinical spectrum of sickle cell disease in Indian context and prenatal diagnosis.

Compound Heterozygosity of β-Thalassemia and the Sickle Cell Hemoglobin in Various Populations of Chhattisgarh State, India

Hemoglobinopathies evolved as a protective mechanism against malaria, which exhibit selective advantage in the heterozygous state. However, in a homozygous recessive condition, it poses a serious socioeconomic burden. Sickle cell anemia is an autosomal recessive hemoglobinopathy associated with erythrocytes sickling, vaso-occlusive crisis (VOC), as well as multi-organ failure and death. The coinheritance of other hemoglobinopathies is known to substantially modulate the clinical manifestation of sickle cell anemia. In the present study, we aimed to analyze the coinheritance of β-thalassemia (β-thal) in Hb S (HBB: c.20A>T) patients. The study includes 918 sickle cell anemia patients from 10 ethnic populations of Chhattisgarh State, India. Complete blood counts (CBCs) and hemoglobin (Hb) high performance liquid chromatography (HPLC) fractionation data were collected from patient record books. We observed Hb S-β-thal in all the analyzed populations. Interestingly, high frequencies of Hb S-β-thal have been observed in Satnami (53.8%), Rawat (47.1%), Gond (35.1%) and Panika (30.6%) populations. Inter-population comparison of hematological parameters [Hb F (p < 0.001), Hb A₂ (p < 0.001), Hb (p = 0.03) and red blood cell distribution width (RDW) (p < 0.001)] revealed significant differences. We also observed that mean Hb F levels were significantly higher in Hb S compared to Hb S-β-thal patients in the respective populations. Our study highlights the higher prevalence of β-thal as well as the compound heterozygosity for Hb S and β-thal in various populations of Chhattisgarh State, India.

Effect of Assorted Globin Haplotypes and α-Thalassemia on the Clinical Heterogeneity of Hb S-β-Thalassemia

Hemoglobinopathies and thalassemias are the most commonly encountered monogenic disorders of blood in humans, posing a major genetic and public health problem round the globe. Hb S (HBB: c.20A>T)-β-thalassemia (β-thal) is a compound aberrant heterozygosity with inconsistent phenotypic expression, which are poorly described and clinically mapped. Comprehensive genetic characterization of such a population is highly warranted for complete understanding of the clinical heterogeneity, disease prognosis and therapeutic management. In this study, Hb S-β-thal (n = 60) patients, strictly defined by varying degrees of clinical presentations, were selected to evaluate their genotype-phenotype agreement. Furthermore, β-globin (n = 120) and α-globin gene clusters (n = 60) were genetically characterized and statistically correlated with clinical terminologies to explain the clinical heterogeneity. Our results revealed the association of the Arab-Indian haplotypes with nine different frameworks of β-thal together with the modulating role of α-thalassemia (α-thal). The study subjects, including carriers of β-thal haplotype III [- - - - - - -] (8.0%), presented with varying severe patterns of clinical symptoms such as painful crisis, multiple infections and splenomegaly, as an outcome of significantly less Hb F and higher Hb S levels (p < 0.5). The study findings indicated that together with α-thal, β-thal haplotypes and Hb F levels, may possibly provide a close justification to support the clinical heterogeneity in the study population.

Adverse clinical and obstetric outcomes among pregnant women with different sickle cell disease genotypes

OBJECTIVE

To compare clinical and obstetric adverse events among pregnant women with sickle cell disease (SCD) according to genotype.

METHODS

The present cross-sectional study enrolled women aged 15-49 years with SCD and prior pregnancy attending a hematology center in Recife, Brazil, between September 1, 2015, and April 30, 2016. Associations between sickle cell genotype (HbSS, HbSC, Sβ-thalassemia) and adverse events were evaluated.

RESULTS

Overall, 89 women were included; 74 (83%) had HbSS genotype, 8 (9%) had HbSC genotype, and 7 (8%) had Sβ-thalassemia genotype. Fifty-three (60%) self-reported being of mixed race, and 27 (30%) self-reported they were black. Blood transfusion was observed more frequently among women with HbSS than among those with HbSC genotype (P=0.007). Postpartum adverse events were more frequent in the Sβ-thalassemia than in the HbSS group (P=0.030). Fetal intrauterine death occurred only among women with the HbSS genotype (11 [15%]). In the HbSS group, there was a higher frequency of blood transfusion (P=0.004) and lower rate of spontaneous abortion (P=0.001) among women with six or more consultations.

CONCLUSION

The HbSS genotype was associated with a higher frequency of blood transfusion. Sβ-thalassemia was associated with a higher frequency of postpartum adverse events. Prenatal care was associated with a lower rate of spontaneous abortion in the HbSS group.

Sickle cell disease

Sickle cell disease (SCD) is a group of inherited disorders caused by mutations in HBB, which encodes haemoglobin subunit β. The incidence is estimated to be between 300,000 and 400,000 neonates globally each year, the majority in sub-Saharan Africa. Haemoglobin molecules that include mutant sickle β-globin subunits can polymerize; erythrocytes that contain mostly haemoglobin polymers assume a sickled form and are prone to haemolysis. Other pathophysiological mechanisms that contribute to the SCD phenotype are vaso-occlusion and activation of the immune system. SCD is characterized by a remarkable phenotypic complexity. Common acute complications are acute pain events, acute chest syndrome and stroke; chronic complications (including chronic kidney disease) can damage all organs. Hydroxycarbamide, blood transfusions and haematopoietic stem cell transplantation can reduce the severity of the disease. Early diagnosis is crucial to improve survival, and universal newborn screening programmes have been implemented in some countries but are challenging in low-income, high-burden settings.

Prenatal Screening for Rare Co-Inheritance of HbE and β-Thalassaemia Traits in Western India

The mutations in Haemoglobin Beta (HBB) gene, bring about less or no production of Hb β-chain synthesis in affected cases, leading from minor to major types depending on haematological indices. In compound heterozygotic conditions, two traits are involved, in which one parent has HbE trait and the other has β-thalassaemia carrier (trait). Here, we report a family of Rajasthan, West India which had a proband (son) having HbE/ β-thalassaemia a co-inherited compound heterozygosity as revealed by DNA sequencing. It also contained upper levels of HbE with altered Hb and red cell indices showing asymptomatic to symptomatic state requiring blood transfusion periodically. The parents and Chorionic Villus Sampling (CVS) were HbE and β-thalassaemia traits only. Such case is rare in Western India and we recommend this family for genetic counseling and genetic testing before they want reproductive choices in future for better management in a society.

The Sickle β-Thalassemia Phenotype

Sβ-thalassemia (Sβ-thal) is common among Gulf Arab patients with sickle cell disease, but the phenotype of this group had not been well-documented. We have studied a group of Kuwaiti patients and compared the phenotype in the homozygotes (SS) and Sβ-thal patients. Complete blood count, hemoglobin quantitation, serum bilirubin, and lactate dehydrogenase were determined with standard techniques. The patients were screened for α-globin genotype. The Sβ-thal patients were also screened for the HBG2 Xmn-1 polymorphism. β-Thal mutations were determined by arrayed primer extension or direct sequencing. There were 70 SS and 32 Sβ-thal patients with mean ages of 14.8±5.9 and 14.2±5.9 years, respectively. The Sβ-thal patients had more frequent, severe pain episodes per year compared with the SS, while the patterns among Sβ-thal and Sβ-thal patients were not significantly different. There were no differences in the frequencies of acute chest syndrome, gallstones, and blood transfusion in the SS and Sβ-thal patients. However, none of the Sβ-thal patients had been transfused. Among the Sβ-thal patients, 25 had β-thal and 7 had β-thal mutations, the most common being cd39 (C→T) and IVS-I-110 (G→A), respectively. Sβ-thal shows a severe phenotype in Kuwait, even among those with Sβ-thal, in whom the IVS-I-110 (G→A) mutation is predominant.

Detection of Compound Heterozygous Sickle Cell-β+ Thalassaemia in a Patient with Extreme Weakness, Mild Jaundice and Moderate Anaemia - A Case Report

A 16-year-old female complained of extreme weakness. She had moderate anaemia; her Haemoglobin (Hb) was 7.7 gm/dl. Peripheral blood smear showed few sickled red cells. Sickle cell test was positive. High-Performance Liquid Chromatography (HPLC) revealed elevated levels of HbS (38.4%) and HbF (15.7%). In addition, HbA2 concentration was 3.8% and HbA concentration was 42.1%. Results suggested a diagnosis of compound heterozygous sickle cell-β+ thalassaemia. Sickle cell test was also positive with blood of patient's brother; Hb HPLC examination showed relatively low concentration of HbS (25.2%) suggesting a diagnosis of sickle cell trait. Chromatogram of patient's step sister suggested a diagnosis of thalassaemia trait. Findings of this study suggested that abnormal genes were inherited in the patient from both the parents. It was interpreted that repeated haemolysis in the patient might have contributed to anaemia, weakness, rise in indirect bilirubin and jaundice. Furthermore, high level of HbF (>12%) may interfere with polymerization of sickle haemoglobin suggesting beneficial effects of HbF-inducing agents which may inhibit sickling.

Coinheritance of B-Thalassemia and Sickle Cell Anaemia in Southwestern Nigeria

BACKGROUND

Genes for haemoglobin S are found in high frequencies in Nigeria. However, there is little information on beta thalassemia in sickle cell anaemia in this population. The clinical presentation of HbS- β thalassemia is enormously variable, ranging from an asymptomatic state to a severe disorder similar to homozygous sickle cell disease.

MATERIALS AND METHODS

Haemoglobin A2 and HbF were determined in sickle cell anaemia patients attending LAUTECH Teaching Hospital, Osogbo, by elution after electrophoresis and alkaline denaturation methods respectively. Haematological parameters were estimated using Sysmex KX-21N and percentage target cells using Leishman's staining technique.

RESULTS

Exactly 6% f the SCA patients were found to have elevated HbA2 (>3.3%) and HbF (>1.3%). These patients also had normal erythrocyte indices, increased platelet count, a significantly higher HCT and an increased % target cell.

CONCLUSION

These findings confirm that the frequency of beta thalassaemia in sickle cell patients in Nigeria is higher than previously thought. It is therefore important to consider the possibility of this variant in patients with sickle cell anaemia since their course may differ from that of patients with homozygous sickle cell anaemia.

Clinical events in a large prospective cohort of children with sickle cell disease in Nagpur, India: evidence against a milder clinical phenotype in India

BACKGROUND

The clinical phenotype of sickle cell disease (SCD) has been reported to be milder in India than in the United States. The objective of this large single-center study was to examine the rate of complications to define the phenotype of SCD in India.

METHODS

The rate of complications per 100 person-years in 833 pediatric SCD patients for 1954 person-years in Nagpur, India including those diagnosed on newborn screen (NBS) and those presenting later in childhood (non-NBS) was compared to those reported in the cooperative study of sickle cell disease (CSSCD). Event rates were also compared between patients belonging to scheduled castes (SCs), scheduled tribes (STs), and other backward classes (OBC).

RESULTS

Comparison of CSSCD versus Nagpur NBS versus Nagpur non-NBS for rates of pain (32.4 vs. 85.2 vs. 62.4), severe anemia (7.1 vs. 27 vs. 6.6), stroke (0.7 vs. 0.8 vs. 1.4), splenic sequestration (3.4 vs. 6.7 vs. 1.6), acute chest syndrome (24.5 vs. 23.6 vs. 1.0), and meningitis (0.8 vs. 0 vs. 0.1) revealed more frequent complications in Nagpur compared to CSSCD. Comparison of ST, SC, and OBC for rates of pain (84.6 vs. 71.9 vs. 63.5), acute chest syndrome (3.6 vs. 2.8 vs. 2.2), severe anemia (5.4 vs. 9.5 vs. 11.4), stroke (1.2 vs. 0.4 vs. 0.3), splenic sequestration (0.6 vs. 2.4 vs. 1.9), and meningitis (0.8 vs. 0 vs. 0.1) revealed significantly more frequent complications among ST.

CONCLUSIONS

SCD-related complications are more frequent in Indian children than that observed in CSSCD. Further study is indicated to define SCD phenotype in India.

Sickle cell disease in tribal populations in India

The sickle gene is widespread among many tribal population groups in India with prevalence of heterozygotes varying from 1-40 per cent. Co-inheritance of the sickle gene with β-thalassaemia, HbD Punjab and glucose-6-phosphate dehydrogenase (G6PD) deficiency has also been reported. Most of the screening programmes in India now use high performance liquid chromatography (HPLC) analysis although the solubility test is also sensitive and cheap. Sickle cell disease (SCD) among tribal populations is generally milder than among non-tribal groups with fewer episodes of painful crises, infections, acute chest syndrome and need for hospitalization. This has partly been attributed to the very high prevalence of α-thalassaemia among these tribes as well as higher foetal haemoglobin levels. However, the clinical presentation is variable with many cases having a severe presentation. There is not much information available on maternal and perinatal outcome in tribal women with sickle cell disease. Newborn screening programmes for SCD have recently been initiated in Maharashtra, Gujarat, Odisha and Chattisgarh and monitoring these birth cohorts will help to understand the natural history of SCD in India. Prenatal diagnosis is acceptable by tribal families in India. The Indian Council of Medical Research and the National Rural Health Mission in different States are undertaking outreach programmes for better management and control of the disease.

Co-inheritance of sickle cell trait and thalassemia mutations in South central iran

BACKGROUND

We aimed to determine the incidence of co-inheritance as well as interaction of sickle cell trait (SCT) and α(thal)/β(thal) mutations in south and south central of Iran.

METHOD

We employed a PCR and restriction fragment length polymorphism techniques to confirm diagnosis of sickle cell trait. All subjects were screened for any α/β -thalassemia mutations using a gap-polymerase chain reaction and amplification refractory mutations system.

RESULTS

Our results showed combination of sickle cell trait and β-globin mutation results in a severe clinical course of similar to sickle cell disease, while coinheritance of α-globin gene defects usually modulates the clinical course. A coexistence of sickle cell trait and α-globin gene mutation was the frequent genotype in overall samples (57. 5%).

CONCLUSION

Sickle cell trait mainly co-inherits with α-globin gene mutation in the south and south central region of Iran. This combination modulates hematological indices and interferes with the SCT diagnosis.

Molecular characterization of hemoglobin D Punjab traits and clinical-hematological profile of the patients

CONTEXT AND OBJECTIVE

Hemoglobin (Hb) D hemoglobinopathies are widespread diseases in northwestern India and usually present with mild hemolytic anemia and mild to moderate splenomegaly. The heterozygous form of Hb D is clinically silent, but coinheritance of Hb D with Hb S or beta-thalassemia produces clinically significant conditions like thalassemia intermedia of moderate severity. Under heterozygous conditions with coinheritance of alpha and beta-thalassemia, patients show a degree of clinical variability. Thus, our aim was to molecularly characterize the Hb D trait among individuals who were clinically symptomatic because of co-inheritance of alpha deletions or any beta-globin gene mutations.

DESIGN AND SETTING

This was a cross-sectional study conducted in an autonomous tertiary-care hospital.

METHODS

Complete blood count and red cell indices were measured using an automated cell analyzer. Quantitative assessment of hemoglobin Hb F, Hb A, Hb A2 and Hb D was performed by means of high performance liquid chromatography (HPLC). DNA extraction was done using the phenol-chloroform method. Molecular analyses on common alpha deletions and common beta mutations were done using the Gap polymerase chain reaction and Amplification Refractory Mutation System, respectively.

RESULTS

We evaluated 30 patients and found clinical variation in the behavior of Hb D traits. In six patients, the Hb D traits were clinically symptomatic and behaved like those of thalassemia intermedia. Molecular characterization showed that three out of these six were IVS-1-5 positive.

CONCLUSIONS

HPLC may not be the gold standard for diagnosing symptomatic Hb D Punjab traits. Hence, standard confirmation should include molecular studies.