Clinical and molecular characteristics of sickle cell anemia in the northeast of Brazil

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.

Ancestry, diversity, and genetics of health-related traits in African-derived communities (quilombos) from Brazil

Brazilian quilombos are communities formed by enslaved Africans and their descendants all over the country during slavery and shortly after its abolition. Quilombos harbor a great fraction of the largely unknown genetic diversity of the African diaspora in Brazil. Thus, genetic studies in quilombos have the potential to provide important insights not only into the African roots of the Brazilian population but also into the genetic bases of complex traits and human adaptation to diverse environments. This review summarizes the main results of genetic studies performed on quilombos so far. Here, we analyzed the patterns of African, Amerindian, European, and subcontinental ancestry (within Africa) of quilombos from the five different geographic regions of Brazil. In addition, uniparental markers (from the mtDNA and the Y chromosome) studies are analyzed together to reveal demographic processes and sex-biased admixture that occurred during the formation of these unique populations. Lastly, the prevalence of known malaria-adaptive African mutations and other African-specific variants discovered in quilombos, as well as the genetic bases of health-related traits, are discussed here, together with their implication for the health of populations of African descent.

Leg Ulcers in Sickle Cell Disease: A Multifactorial Analysis Highlights the Hemolytic Profile

Sickle cell disease (SCD) is characterized by the presence of the variant S hemoglobin (HbS). The homozygous genotype (HbSS) is sickle cell anemia (SCA), while the double heterozygous of HbS and HbC (HbSC) is defined as SC hemoglobinopathy. The pathophysiology is based on chronic hemolysis, inflammation, endothelial dysfunction, and vaso-occlusion, which results in vasculopathy and serious clinical manifestations. Sickle leg ulcers (SLUs) are cutaneous lesions around the malleoli frequent in 20% of Brazilian patients with SCD. SLUs present a variable clinical and laboratory pattern modulated by several characteristics that are not fully understood. Hence, this study aimed to investigate laboratory biomarkers and genetic and clinical parameters associated with the development of SLUs. This descriptive cross-sectional study included 69 SCD patients, 52 without SLU (SLU-) and 17 with active or previous SLU history (SLU+). The results showed a higher incidence of SLU in SCA patients and there was no observed association of α-3.7 Kb thalassemia in SLU occurrence. Alterations in NO metabolism and hemolysis were associated with clinical evolution and severity of SLU, in addition to hemolysis modulating the etiology and recurrence of SLU. Our multifactorial analyses demonstrate and extend the role of hemolysis driving the pathophysiological mechanism of SLU.

Sickle cell disease in Gulf Cooperation Council countries: a systematic review

INTRODUCTION

Evidence related to the national burden of Sickle Cell Disease (SCD) in Gulf Cooperation Council (GCC) largely fragmented. Thus, the aim of this study is to systemically review studies from GCC countries to assess the epidemiological profile of SCD.

AREAS COVERED

We searched combinations of key terms in MEDLINE/PubMed, CINAHL, and EMBASE. We selected relevant observational studies reporting the frequency, incidence, prevalence, risk factors, mortality rate, and complications of SCD among the GCC population. Studies restricted to laboratory diagnostic tests, experimental and animal studies, review articles, case reports and series, and conference proceedings and editorials were excluded. A total of 1,347 articles were retrieved, out of which 98 articles were found to be eligible and included in the study. The total number of participants from all the included studies was 3496447. The prevalence of SCD ranged from 0.24%-5.8% across the GCC and from 1.02%-45.8% for the sickle cell trait. Consanguineous marriage was a risk factor for likely giving children affected with hemoglobinopathies.

EXPERT OPINION

The prevalence of SCD and its complications vary among GCC. Because of the high prevalence of SCD and its complications, health authorities should focus on more rigorous prevention and treatment strategies.

Alpha thalassemia, but not βS-globin haplotypes, influence sickle cell anemia clinical outcome in a large, single-center Brazilian cohort

Alpha thalassemia and beta-globin haplotype are considered classical genetic disease modifiers in sickle cell anemia (SCA) causing clinical heterogeneity. Nevertheless, their functional impact on SCA disease emergence and progression remains elusive. To better understand the role of alpha thalassemia and beta-globin haplotype in SCA, we performed a retrospective study evaluating the clinical manifestations of 614 patients. The univariate analysis showed that the presence of alpha-thalassemia -3.7-kb mutation (αα/-α and -α/-α) decreased the risk of stroke development (p = 0.046), priapism (p = 0.033), and cholelithiasis (p = 0.021). Furthermore, the cumulative incidence of stroke (p = 0.023) and cholelithiasis (p = 0.006) was also significantly lower for patients carrying the alpha thalassemia -3.7-kb mutation. No clinical effects were associated with the beta-globin haplotype analysis, which could be explained by the relatively homogeneous haplotype composition in our cohort. Our results reinforce that alpha thalassemia can provide protective functions against hemolysis-related symptoms in SCA. Although, several genetic modifiers can impact the inflammatory state of SCA patients, the alpha thalassemia mutation remains one of the most recurrent genetic aberration and should therefore always be considered first.

Sickle cell anemia in the state of Maranhão: a haplotype study

Sickle cell anemia (SCA) is the most severe form of sickle cell disease caused by homozygosity of the β^S-gene (S/S or β^Sβ^S) and has worldwide distribution. Six polymorphic sites in the β-globin gene cluster were analyzed from a sample of 56 chromosomes of patients with SCA from the state of Maranhão, northeastern Brazil. PCR-RFLP showed that the CAR haplotype was predominant with a frequency of 64.28%, followed by the BEN haplotype (28.57%). Atypical haplotypes were identified at a frequency of 7.15%. Genotypes CAR/CAR, BEN/BEN, and CAR/BEN were present in 46.43%, 10.71%, and 35.71% of patients, respectively. β-Globin haplotype determination is important not only for the monitoring and prognosis of patients with SCA, but it also serves to inform anthropological studies that contribute to elucidating any peculiarities associated with African influences that contributed to the ethnological, economic, cultural, and social formation of Brazil. The high frequency of the CAR/CAR and CAR/BEN haplotypes in this study, which are associated with low levels of fetal hemoglobin, may ultimately reflect a severe clinical course and poor prognosis in patients with SCA in Maranhão.

Presencia de haplotipos no africanos incrementa la diversidad genética en pacientes con anemia falciforme en Colombia

El objetivo de este estudio fue identificar la frecuencia de haplotipos dentro del cluster de Beta globina presente en pacientes con anemia falciforme en Colombia, establecer la presencia de haplotipos no africanos en esta población, así como verificar variaciones en el patrón de desequilibrio de ligamiento dentro del cluster de Beta globina. Se analizaron 83 individuos con anemia falciforme, los haplotipos se formaron utilizando cinco sitios de restricción dentro del cluster de Beta globina, se estableció la frecuencia de haplotipos, se calculó el grado de desequilibrio de ligamiento entre los sitios de restricción, así como la similitud genética de esta población con otra de afectados en América. Los haplotipos más frecuentes en la población fueron Benín ( 35,1 %) y Bantú (26, 5 %), ambos africanos. Sin embargo, haplotipos presentes en poblaciones indígenas americanas y europeas alcanzaron frecuencias entre el 2 – 10 %, así como haplotipos que no han sido reportados en otras poblaciones. Los sitios de restricción presentaron bajo o nulo desequilibrio de ligamiento entre ellos. Al compararse con otras poblaciones, la población colombiana presentó mayor similitud con la población de Venezuela en donde Benin y Bantú son también predominantes. Nuestros resultados muestran que el mestizaje ha facilitado el paso de la mutación para la anemia falciforme a un contexto genético no africano (amerindio y europeo). Además, el mestizaje también ha alterado el patrón de desequilibrio de ligamiento dentro del cluster de Beta globina generando modificaciones que pueden tener influencia en estudios de asociación dentro de esta población de afectados. 

Influence of alpha thalassemia on clinical and laboratory parameters among nigerian children with sickle cell anemia

BACKGROUND

There is paucity of data on the influence of alpha thalassemia on the clinical and laboratory parameters among Nigerian sickle cell anemia (SCA) patients. This study aimed to determine the prevalence of alpha thalassemia and the influence of alpha thalassemia on laboratory parameters and clinical manifestations in a group of young Nigerian SCA patients.

METHODS

This was a cross-sectional retrospective study conducted on 100 patients with SCA and 63 controls. The diagnosis of SCA was confirmed by DNA studies. Alpha thalassemia genotyping was performed by multiplex gap-PCR method. Laboratory parameters including complete blood count, hemoglobin quantitation, serum lactate dehydrogenase (LDH), and bilirubin were determined with standard techniques.

RESULTS

Alpha thalassemia was found in 41 (41.0%) patients compared to 24 (38.1%) controls (P = 0.744), and all were due to the 3.7 κb α-globin gene deletions. Alpha thalassemia was associated with more frequent bone pain crisis, higher hemoglobin concentration, red blood cell count, and HbA₂ level among the patients. On the contrary, patients with alpha thalassemia had lower mean corpuscular volume, mean corpuscular hemoglobin, and white blood cell count (WBC) (P ˂ 0.05). There were 6 (6.0%) patients with leg ulcers, and none of them had alpha thalassemia, P = 0.04.

CONCLUSION

This study confirms that coexistence of alpha thalassemia with SCA significantly influences both the clinical and laboratory manifestations of young Nigerian SCA patients. The coexistence of this genetic modifier is associated with increased bone pain crisis and protects against sickle leg ulcers among the patients.

Evaluation of hematological indices of childhood illnesses in Tamale Metropolis of Ghana

BACKGROUND

Although hematological indices cannot in entirety be used to diagnose diseases or defects, the appropriate interpretation of these indices could complement diagnostics such as microscopy and serology for numerous illnesses in children. This study sought to evaluate distinct hematological indices characterizing different childhood illnesses.

METHODS

Full blood counts from 150 children (age range from 1 to 15 year) presenting different disease conditions at the Tamale Central Hospital were assessed. The hematological indices were compared between disease categories, and relationships between disease indicators were determined.

RESULTS

The prevalence of the diagnosed childhood illness were: 50.7% malaria, 20.0% diarrhea, 13.3% typhoid fever, 10.0% Sickle Cell Disease (SCD), and 6.0% malaria-typhoid co-infection. Fever was diagnosed in a majority (66.0%) of the children, but was independent of each disease group, (χ²  = 9.18, P = .057). Of the 24 hematological indices analyzed, eight; red blood cell (RBC) (P < .001), hemoglobin (Hb) (P < .001), mean cell volume (MCV) (P = .002), mean cell hemoglobin (MCH) (P < .001; lowest and below normal range for SCD), red cell distribution width (RDW_CV) (P < .001), eosinophil percentage [EOS (%)] (P = .001), eosinophil number [EOS#] (P = .002), and platelets (PLT) (P = .001; lowest for malaria) differed significantly across the different disease groups. Levels of Hb and/or MCV were below the normal reference ranges for most of the diagnosed diseases. In addition, low PLT and MCH were respectively distinct for children with malaria and SCD.

CONCLUSION

Hematological indices including Hb, MCV and PLT, or MCH may be useful indices that could incite further diagnostic tests for malaria or SCD among children in Ghana.

The effects of old and recent migration waves in the distribution of HBB*S globin gene haplotypes

Sickle cell hemoglobin is the result of a mutation at the sixth amino acid position of the beta (β) globin chain. The HBB*S gene is in linkage disequilibrium with five main haplotypes in the β-globin-like gene cluster named according to their ethnic and geographic origins: Bantu (CAR), Benin (BEN), Senegal (SEN), Cameroon (CAM) and Arabian-Indian (ARAB). These haplotypes demonstrated that the sickle cell mutation arose independently at least five times in human history. The distribution of βS haplotypes among Brazilian populations showed a predominance of the CAR haplotype. American populations were clustered in two groups defined by CAR or BEN haplotype frequencies. This scenario is compatible with historical records about the slave trade in the Americas. When all world populations where the sickle cell gene occurs were analyzed, three clusters were disclosed based on CAR, BEN or ARAB haplotype predominance. These patterns may change in the next decades due to recent migrations waves. Since these haplotypes show different clinical characteristics, these recent migrations events raise the necessity to develop optimized public health programs for sickle cell disease screening and management.

Beta-globin gene haplotypes among cameroonians and review of the global distribution: is there a case for a single sickle mutation origin in Africa?

Studies of hemoglobin S haplotypes in African subpopulations have potential implications for patient care and our understanding of genetic factors that have shaped the prevalence of sickle cell disease (SCD). We evaluated HBB gene cluster haplotypes in SCD patients from Cameroon, and reviewed the literature for a global distribution. We reviewed medical records to obtain pertinent socio-demographic and clinical features for 610 Cameroonian SCD patients, including hemoglobin electrophoresis and full blood counts. RFLP-PCR was used to determine the HBB gene haplotype on 1082 chromosomes. A systematic review of the current literature was undertaken to catalogue HBB haplotype frequencies in SCD populations around the world. Benin (74%; n = 799) and Cameroon (19%; n = 207) were the most prevalent haplotypes observed among Cameroonian patients. There was no significant association between HBB haplotypes and clinical life events, anthropometric measures, hematological parameters, or fetal hemoglobin (HbF) levels. The literature review of the global haplotype distributions was consistent with known historical migrations of the people of Africa. Previously reported data from Sudan showed a distinctly unusual pattern; all four classical haplotypes were reported, with an exceptionally high proportion of the Senegal, Cameroon, and atypical haplotypes. We did not observe any significant associations between HBB haplotype and SCD disease course in this cohort. Taken together, the data from Cameroon and from the wider literature suggest that a careful reassessment of African HBB haplotypes may shed further light on the evolutionary dynamics of the sickle allele, which could suggest a single origin of the sickle mutation.

Α-Thalassemia: Genotypic Profile Associated with Ethnicity and Hematological Differentiation of Iron Deficiency Anemia in the Region of Uberaba, Minas Gerais, Brazil

α-Thalassemia (α-thal) is a hereditary hemoglobinopathy characterized by microcytic anemia due to impaired production of α chains of human globin. Brazilian studies show that the most common genotype is an -α(3.7) deletion with the loss of one or two α genes. As the production of α chains is not as accentuated in these cases, the correct diagnosis can only be achieved through molecular analysis that is not usually routinely performed by laboratories. We investigated the occurrence of α-thal babies born between September 2011 to January 2013 at the hospital of the Universidade Federal do Triângulo Mineiro (UFTM), Uberaba, Brazil, and blood donors of the Uberaba Regional Blood Center, Hemominas Foundation, Uberaba, Brazil, correlating it with ethnicity and differences between hematological parameters of donors, α-thal and iron deficiency patients. α-Thalassemia was investigated for the most common deleted alleles (-α(3.7), -α(4.2), - -(SEA), - -(FIL), - -(THAI), -(α)(20.5) and - -(MED)). The incidence in newborns was 13.16% with a predominance of heterozygosity for the -α(3.7) genotype (12.35%), followed by the -α(3.7)/-α(3.7) (0.46%) and αα/-α(4.2) genotypes (0.35%). In blood donors, the prevalence of α-thal was 14.89%, with all cases being heterozygous for the -α(3.7) deletion. There was an association of the α-thal genotype with African ancestors for both groups, thereby confirming published data and showing the strong influence of Blacks on the composition of the population of Brazil's southeastern region. Minor changes were found between hematological parameters of blood donors with iron deficiency and α-thal that did not contribute to the differential diagnosis between the two types of anemia.

Efficacy of autologous stem cell-based therapy for osteonecrosis of the femoral head in sickle cell disease: a five-year follow-up study

INTRODUCTION

Stem cell therapy with bone marrow-derived mononuclear cells (BMMCs) is an option for improving joint function in osteonecrosis of the femoral head (ONFH). Bone marrow-derived mesenchymal stromal cell (MSC) numbers and their osteogenic differentiation are decreased in patients with ONFH. However, whether this decrease also extends to the early stages of ONFH in sickle cell disease (SCD) is still unclear.

METHODS

We conducted a phase I/II, non-controlled study to determine efficacy and safety of BMMC implantation using a minimally invasive technique in SCD patients with ONFH. Eighty-nine patients were recruited and followed up for 60 months after surgery. Clinical and radiographic findings were assessed, and data were completed by in vitro analysis.

RESULTS

At the final follow-up (60 months) there was a significant improvement in clinical joint symptoms and pain relief as measured by the Harris Hip Score (P = 0.0005). In addition, after the BMMC implantation procedure, radiographic assessment showed disease stabilization and only 3.7 % of the treated patients did not achieve a satisfactory clinical result. The amount of fibroblast colony-forming units was 28.2 ± 13.9 per 1 million BMMCs after concentration. Flow cytometry analysis showed a significantly higher number of hematopoietic stem/endothelial progenitor cell markers in concentrated BMMCs when compared with bone marrow aspirate, indicating an enrichment of these cell types. Isolated MSCs from SCD patients with pre-collapse ONFH maintained the replicative capacity without significant loss of their specific biomolecular characteristics, multi-differentiation potential, and osteogenic differentiation activities. Cytokines and growth factors (interleukin-8, transforming growth factor-beta, stromal cell-derived factor-1alpha and vascular endothelial growth factor) that mediate endogenous bone regeneration were also produced by expanded MSCs from SCD patients.

CONCLUSION

The autologous BMMC implantation with a minimally invasive technique resulted in significant pain relief and halted the progression of early stages of ONFH in SCD patients. MSCs from SCD patients display biological properties that may add to the efficiency of surgical treatment in ONFH. In summary, our results indicate that infusion of BMMCs enriched with stem/progenitor cells is a safe and effective treatment for the early stages of ONFH in SCD patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02448121; registered 15 May 2015.

Pattern of hemolysis parameters and association with fetal hemoglobin in sickle cell anemia patients in steady state

Objective

This study aimed to evaluate the influence of fetal hemoglobin (Hb F) on hemolysis biomarkers in sickle cell anemia patients.

Methods

Fifty adult sickle cell anemia patients were included in the study. All patients were taking hydroxyurea for at least six months and were followed at the outpatient clinic of a hospital in Fortaleza, Ceará, Brazil. The control group consisted of 20 hemoglobin AA individuals. The reticulocyte count was performed by an automated methodology, lactate dehydrogenase and uric acid were measured by spectrophotometry and arginase I by enzyme-linked immunosorbent assay (ELISA). The presence of Hb S was detected by high-performance liquid chromatography. The level of significance was set for a p-value <0.05.

Results

A significant increase was observed in the reticulocyte count and lactate dehydrogenase, uric acid and arginase I levels in sickle cell anemia patients compared to the control group (p-value <0.05). Patients having Hb F levels greater than 10% showed a significant decrease in the reticulocyte count, arginase I and lactate dehydrogenase. A significant decrease was observed in arginase I levels in patients taking hydroxyurea at a dose greater than 20 mg/kg/day.

Conclusion

The results of this study show that sickle cell anemia patients have increases in the hemolysis biomarkers, lactate dehydrogenase, reticulocyte count, arginase I, uric acid and increases in Hb F can reduce the reticulocyte count and arginase I and lactate dehydrogenase levels.

Molecular analysis and association with clinical and laboratory manifestations in children with sickle cell anemia

OBJECTIVES

To analyze the frequency of β(S)-globin haplotypes and alpha-thalassemia, and their influence on clinical manifestations and the hematological profile of children with sickle cell anemia.

METHOD

The frequency of β(S)-globin haplotypes and alpha-thalassemia and any association with clinical and laboratorial manifestations were determined in 117 sickle cell anemia children aged 3-71 months. The confirmation of hemoglobin SS and determination of the haplotypes were achieved by polymerase chain reaction-restriction fragment length polymorphism, and alpha-thalassemia genotyping was by multiplex polymerase chain reaction (single-tube multiplex-polymerase chain reaction).

RESULTS

The genotype distribution of haplotypes was 43 (36.7%) Central African Republic/Benin, 41 (35.0%) Central African Republic/Central African Republic, 20 (17.0%) Rare/atypical, and 13 (11.1%) Benin/Benin. The frequency of the α3.7 deletion was 1.71% as homozygous (-α3.7/-α3.7) and 11.9% as heterozygous (-α3.7/αα). The only significant association in respect to haplotypes was related to the mean corpuscular volume. The presence of alpha-thalassemia was significantly associated to decreases in mean corpuscular volume, mean corpuscular hemoglobin and reticulocyte count and to an increase in the red blood cell count. There were no significant associations of β(S)-globin haplotypes and alpha-thalassemia with clinical manifestations.

CONCLUSIONS

In the study population, the frequency of alpha-thalassemia was similar to published data in Brazil with the Central African Republic haplotype being the most common, followed by the Benin haplotype. β(S)-globin haplotypes and interaction between alpha-thalassemia and sickle cell anemia did not influence fetal hemoglobin concentrations or the number of clinical manifestations.

Patients with sickle cell disease taking hydroxyurea in the Hemocentro Regional de Montes Claros

Background

The development of therapies for sickle cell disease has received special attention, particularly those that reduce the polymerization of hemoglobin S. Hydroxyurea is a commonly used medication because it has the ability to raise levels of fetal hemoglobin, decrease the frequency of vaso-occlusive episodes and thus improve the clinical course of sickle cell disease patients.

Objective

To study hematological data and the clinical profile of sickle cell disease patients taking hydroxyurea in a regional blood center.

Methods

From the charts of 20 patients with sickle cell anemia, the clinical outcomes and a number of hematological variables were analyzed before and during treatment with hydroxyurea.

Results

The patients' ages ranged from 6 to 41 years old, most were dark skinned and there was a predominance of women. The main symptom that defined whether patients were prescribed hydroxyurea was painful crises followed by hospitalizations. During treatment with hydroxyurea there were significant increases in hemoglobin, fetal hemoglobin, mean corpuscular volume and mean corpuscular hemoglobin. The reticulocyte and white blood cell counts dropped significantly with treatment. A positive correlation was found between fetal hemoglobin and mean corpuscular volume before and during treatment. Additionally, a correlation was found between the white blood cell and reticulocyte counts before treatment with hydroxyurea.

Conclusion

Most patients showed improvements with treatment as demonstrated by increases in hemoglobin, fetal hemoglobin and mean corpuscular volume, as well as by reductions in the reticulocyte and white blood cell counts. Clinically, more than 50% of patients had a significant reduction of events.

Impact of β(S)-globin haplotypes on oxidative stress in patients with sickle cell anemia in steady state

BACKGROUND AND AIMS

In Brazil, sickle cell anemia (SCA) is one of the most common genetic disorders. The levels of fetal hemoglobin (HbF) may be influenced by the presence of genetic modifiers; among these are the β(S)-globin haplotypes, associated with the clinical heterogeneity presented by the disease. Patients with SCA have an imbalance between the production of reactive oxygen species and antioxidant capacity, generating oxidative stress. Nitric oxide (NO) is a potent vasodilator and may be involved in the mechanism of HbF induction. The aim of this study was to evaluate the impact of β(S)-globin haplotypes in oxidative stress in patients with SCA.

METHODS

The study included 47 patients with SCA in steady state. The molecular diagnosis of SCA and characterization of the β(S)-globin haplotype was performed by β(S) chain polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP). Concentration of HbF was determined by high-performance liquid chromatography (HPLC). Serum levels of nitrite/nitrate (NOx) and malondialdehyde were determined by spectrophotometry.

RESULTS

The most prevalent haplotype in the study population was Bantu. The Benin/n group presented significantly higher HbF and nitrite levels as compared to the Bantu/n group.

CONCLUSIONS

Our results confirm data reported in the literature where the Benin and Bantu haplotypes are respectively correlated to high levels and decreased HbF. In addition, haplotypes associated with high levels of HbF showed high levels of nitrite, demonstrating that as the HbF, serum levels of NOx may prove useful as a prognostic biomarker in patients with SCA.

Inherited hemoglobin disorders in an Afro-Amazonian community: Saracura

The most common hemoglobinopathies, viz, hemoglobins S and C, and α- and β-thalassemias, were investigated through the molecular screening of 116 subjects from the community of Saracura, comprising fugitive African slaves from farms of the municipality of Santarém, in the west of Pará State, Brazilian Amazon. The observed frequency of the HBB*S gene (0.9%) was significantly lower than that encountered in other Afro-derived communities in the region. Concomitantly, the absence of the HBB*C allele has been reported for most of the Afro-Amazonian communities thus far studied. As remnant populations of quilombos are generally small, the heterogeneous distribution of HBB*S and HBB*C alleles among them is probably due to genetic drift and/or founder effect. The observed frequency of 3.7 kb deletion in Saracura (8.5%) was consistent with the African origin of the population, with a certain degree of local differentiation and admixture with individuals of Caucasian ancestry, placed in evidence by the occurrence of - -(MED) deletion (1.2%), a common mutation in Mediterranean regions. As regards β-thalassemia, among the seven different mutations found in Saracura, three β^o and two β⁺ mutations were of Mediterranean origin, and two β⁺ of African. Thus, only 28% of the local β-thalassemia mutations found in Saracura were of African origin.

Genetic polymorphisms and cerebrovascular disease in children with sickle cell anemia from Rio de Janeiro, Brazil

The aim of the present work was to examine possible genetic risk factors related to the occurrence of cerebrovascular disease (CVD) in Brazilian population, the frequency of β(S)-globin gene haplotypes and co-inheritance with α-thalassemia (-α(3.7kb)) and single nucleotide polymorphism of methylenetetrahydrofolate reductase (MTHFR-C677T), Factor V Leiden (FV-G1691A) and prothrombin (PT-G20210A) genes in children from Rio de Janeiro. Ninety four children with sickle cell anemia (SCA) were included, 24 patients with cerebrovascular involvement and 70 patients without CVD as control group. The mean age of children at the time of the cerebrovascular event was similar to the control group. The frequency of -α(3.7kb) thalassemia was similar in both groups (p=0.751). Children with Bantu/Atypical β(S)-globin gene haplotype presented 15 times more chance (OR=15.4 CI 95% 2.9-81.6) of CVD than the other β(S)-globin gene haplotypes. The C677T polymorphism of MTHFR gene was similar in both groups (p=0.085). No mutation in the FV Leiden or PT genes was found. A large study seems necessary to establish the role of these genetic polymorphisms in Brazilian miscegenated population.

Determination of β haplotypes in patients with sickle-cell anemia in the state of Rio Grande do Norte, Brazil

β^S haplotypes were studied in 47 non-related patients with sickle-cell anemia from the state of Rio Grande do Norte, Brazil. Molecular analysis was conducted by PCR/RFLP using restriction endonucleases XmnI, HindIII, HincII and HinfI to analyze six polymorphic sites from the beta cluster. Twenty-seven patients (57.5%) were identified with genotype CAR/CAR, 9 (19.1%) CAR/BEN, 6 (12.8%) CAR/CAM, 1 (2.1%) BEN/BEN, 2 (4.3%) CAR/Atp, 1 (2.1%) BEN/Atp and 1 (2.1%) with genotype Atp/Atp. The greater frequency of Cameroon haplotypes compared to other Brazilian states suggests the existence of a peculiarity of African origin in the state of Rio Grande do Norte.

Coinheritance of α-thalassemia decreases the risk of cerebrovascular disease in a cohort of children with sickle cell anemia

The study estimated α-thalassemia (α-thal) prevalence and assessed its associations with clinical and hematological features in a random sample of Brazilian children with sickle cell anemia (208 Hb SS and 13 Hb S-β⁰-thal). α-Thalassemia genotyping was carried out by multiplex polymerase chain reaction (m-PCR) for seven alleles. Clinical and hematological data were retrieved from the 221 children's medical files. Their ages ranged from 2.5 to 10.4 years. Of the Hb SS children, 27.9% carried -α(3.7)/αα and 1.4% -α(3.7)/-α(3.7). The presence of α-thal was significantly associated with reduction in MCV, MCH, WBC values and reticulocyte counts. No significant association with blood transfusion or acute chest syndrome (ACS), was found. α-Thalassemia genotypes were strongly associated with reduction in risk for cerebrovascular disease (CVD) (conditional and abnormal transcranial Doppler or stroke; p = 0.007). The interaction of α-thal with other modulating factors should be investigated in order to define subphenotypes of the disease and to use them as clinical tools in the follow-up care of patients.

Molecular characterization of sickle cell anemia in the Northern Brazilian state of Pará

To assess alpha+-thalassemia deletion alleles, beta-thalassemia mutations and haplotypes linked to the HBB*S cluster in a sample of 130 unrelated sickle cell anemia (SCA) patients (55% female) from Belém, Pará State, for their possible effects on the patients' survival. -alpha(3.7), -alpha(42), -alpha(20.5), and -(MED) alpha+-thalassemia deletion alleles were investigated using multiplex gap-PCR method. Characterization of beta-thalassemia mutations was made by direct genomic sequencing of the beta-globin gene amplified through polymerase chain reaction (PCR). Haplotypes were determined by analysis of six polymorphic restriction sites [(1) XmnI-5'gammaG, (2) HindIII-gammaG, (3) HindIII-gammaA, (4) HincII-psibeta, (5) HincII-3'psibeta, and (6) HinfI-5'beta] followed by restriction digestion and agarose gel electrophoresis. Twenty-one patients (16%) presented -alpha3.7 thalassemia. Sixteen of those (76%) were heterozygous (-alpha3.7/alphaalpha) and 5 (24%) were homozygous (-alpha3.7/-alpha3.7). -Alpha(4.2), -alpha(20.5) and -(MED) deletions were not found. Nine cases of sickle cell-beta thalassemia were found and four different beta-thal mutations were identified: beta(+) -88 (C>T), 3.8%; beta(+) codon 24 (T > A), 1.5%; beta(+) IVSI-110 (G > A), 0.7% and beta (IVSI-1 (G > A), 0.7%. No differences according to age were observed in -alpha(3.7) deletion, beta-thalassemia and HHB*S haplotypes distribution. Our results suggest that although alpha- and beta-thalassemia and betaS haplotypes may have modulating effect on clinical expression and hematological parameters of SCA, these genetic variables probably have little influence on the subjects' survival.

β-globin haplotypes in normal and hemoglobinopathic individuals from Reconcavo Baiano, State of Bahia, Brazil

Five restriction site polymorphisms in the β-globin gene cluster (HincII-5‘ ε, HindIII-^G γ, HindIII-^A γ, HincII- ψβ1 and HincII-3‘ ψβ1) were analyzed in three populations (n = 114) from Reconcavo Baiano, State of Bahia, Brazil. The groups included two urban populations from the towns of Cachoeira and Maragojipe and one rural Afro-descendant population, known as the “quilombo community”, from Cachoeira municipality. The number of haplotypes found in the populations ranged from 10 to 13, which indicated higher diversity than in the parental populations. The haplotypes 2 (+ - - - -), 3 (- - - - +), 4 (- + - - +) and 6 (- + + - +) on the β^A chromosomes were the most common, and two haplotypes, 9 (- + + + +) and 14 (+ + - - +), were found exclusively in the Maragojipe population. The other haplotypes (1, 5, 9, 11, 12, 13, 14 and 16) had lower frequencies. Restriction site analysis and the derived haplotypes indicated homogeneity among the populations. Thirty-two individuals with hemoglobinopathies (17 sickle cell disease, 12 HbSC disease and 3 HbCC disease) were also analyzed. The haplotype frequencies of these patients differed significantly from those of the general population. In the sickle cell disease subgroup, the predominant haplotypes were BEN (Benin) and CAR (Central African Republic), with frequencies of 52.9% and 32.4%, respectively. The high frequency of the BEN haplotype agreed with the historical origin of the afro-descendant population in the state of Bahia. However, this frequency differed from that of Salvador, the state capital, where the CAR and BEN haplotypes have similar frequencies, probably as a consequence of domestic slave trade and subsequent internal migrations to other regions of Brazil.