Sickle cell disease: acute clinical manifestations in early childhood and molecular characteristics in a group of children in Rio de Janeiro

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.

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.

Retinopathy in Egyptian patients with sickle cell disease: A cross-sectional study

ABSTRACT

Sickle cell disease (SCD) is a disorder that causes red blood cells to become sticky and rigid. Sickle cells can block blood flow in small blood vessels depriving the eye of oxygen and cause damage. This is called sickle retinopathy that can progress to severe proliferative sickle cell retinopathy, bleeding into the eye, detachment of the retina or even loss of vision.To assess ocular manifestations and detect frequency of retinopathy in patients with SCD.Cross-sectional study was conducted on 32 patients with SCD. They were 22 males and 10 females with mean age of 12 years. Routine investigations as well as ophthalmological examination including visual acuity, fluorescein angiography and optical coherence tomography were done.We found that 8 patients (25%) suffered from proliferative retinopathy, 10 patients (31%) showed tortuous retinal veins, while 14 patients (44%) were normal. All patients showed macular thinning on optical coherence tomography examination.We concluded that frequency of retinopathy in patients with SCD is more than expected and it was higher in patients who started transfusion at a later age. More attention should be paid for this problem and close observations and follow up is strongly needed.

Cell and Gene Therapy for Anemia: Hematopoietic Stem Cells and Gene Editing

Hereditary anemia has various manifestations, such as sickle cell disease (SCD), Fanconi anemia, glucose-6-phosphate dehydrogenase deficiency (G6PDD), and thalassemia. The available management strategies for these disorders are still unsatisfactory and do not eliminate the main causes. As genetic aberrations are the main causes of all forms of hereditary anemia, the optimal approach involves repairing the defective gene, possibly through the transplantation of normal hematopoietic stem cells (HSCs) from a normal matching donor or through gene therapy approaches (either in vivo or ex vivo) to correct the patient’s HSCs. To clearly illustrate the importance of cell and gene therapy in hereditary anemia, this paper provides a review of the genetic aberration, epidemiology, clinical features, current management, and cell and gene therapy endeavors related to SCD, thalassemia, Fanconi anemia, and G6PDD. Moreover, we expound the future research direction of HSC derivation from induced pluripotent stem cells (iPSCs), strategies to edit HSCs, gene therapy risk mitigation, and their clinical perspectives. In conclusion, gene-corrected hematopoietic stem cell transplantation has promising outcomes for SCD, Fanconi anemia, and thalassemia, and it may overcome the limitation of the source of allogenic bone marrow transplantation.

Genetic determinants and stroke in children with sickle cell disease

OBJECTIVE

To verify genetic determinants associated with stroke in children with sickle cell disease (SCD).

METHODS

Prospective cohort with 110 children submitted to neonatal screening by the Neonatal Screening Program, between 1998 and 2007, with SCD diagnosis, followed at a regional reference public service for hemoglobinopathies. The analyzed variables were type of hemoglobinopathy, gender, coexistence with alpha thalassemia (α-thal), haplotypes of the beta globin chain cluster, and stroke. The final analysis was conducted with 66 children with sickle cell anemia (SCA), using the chi-squared test in the program SPSS^® version 14.0.

RESULTS

Among children with SCD, 60% had SCA. The prevalence of coexistence with α-thal was 30.3% and the Bantu haplotype (CAR) was identified in 89.2%. The incidence of stroke was significantly higher in those with SCA (27.3% vs. 2.3%; p=0.001) and males (24.1% vs. 9.6%; p=0.044). The presence of α-thal (p=0.196), the CAR haplotype (p=0.543), and socioeconomic factors were not statistically significant in association with the occurrence of stroke.

CONCLUSION

There is a high incidence of stroke in male children and in children with SCA. Coexistence with α-thal and haplotypes of the beta globin chain cluster did not show any significant association with stroke. The heterogeneity between previously evaluated populations, the non-reproducibility between studies, and the need to identify factors associated with stroke in patients with SCA indicate the necessity of conducting further research to demonstrate the relevance of genetic factors in stroke related to SCD.

Prevalence of sickle cell disease in a pediatric population suffering from severe infections: a Congolese experience

Neonatal screening for sickle cell anemia is not a common practice in the Democratic Republic of Congo (DRC). Children with sickle cell disease are known to have an increased risk of infections. We conducted a pilot study to determine the prevalence of sickle cell anemia during episodes of severe infection. A prospective study was conducted from July 2009 to July 2011. The study sites included four public hospitals at Kinshasa, DRC. The study population was selected from the source population using three-stage sampling. A total of 247 children with severe infection were consecutively recruited and screened for sickle cell disease. There were 124 boys (50.2%) and 123 girls (49.8%) with a sex-ratio of 1:1. More than two-thirds of patients (66.0%) were children between 1 and 24 months of age. Among these 247 children, 19 (7.7%) were homozygous sickle cell anemia patients (Hb SS). No patient had received Hemophilus influenzae, streptococcus pneumoniae and salmonella sp vaccines. Sepsis was the most common form of severe infection observed in 44.5% of patients. A total of 19 (7.7%) positive blood cultures were recorded. Most cases were reported in sickle cell patients (15.8%) compared to 6.1% in children who were negative for Hb S [β6(A3)Glu→Val; HBB: c.20A>T] (p > 0.05). Of 247 children with severe infection, approximately 8.0% carried unknown sickle cell anemia mutations. Based on the findings in this study, opportunistic testing for sickle cell anemia is possible and worthwhile in children who present with severe infection in DRC until neonatal screening is universal.

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.