Whole-exome sequencing indicates FLG2 variant associated with leg ulcers in Brazilian sickle cell anemia patients

Controversies in the pathophysiology of leg ulcers in sickle cell disease

Patients with sickle cell disease (SCD) often experience painful vaso-occlusive crises and chronic haemolytic anaemia, as well as various acute and chronic complications, such as leg ulcers. Leg ulcers are characterized by their unpredictability, debilitating pain and prolonged healing process. The pathophysiology of SCD leg ulcers is not well defined. Known risk factors include male gender, poor social conditions, malnutrition and a lack of compression therapy when oedema occurs. Leg ulcers typically start with spontaneous pain, followed by induration, hyperpigmentation, blister formation and destruction of the epidermis. SCD is characterized by chronic haemolysis, increased oxidative stress and decreased nitric oxide bioavailability, which promote ischaemia and inflammation and consequently impair vascular function in the skin. This cutaneous vasculopathy, coupled with venostasis around the ankle, creates an ideal environment for local vaso-occlusive crises, which can result in the development of leg ulcers that resemble arterial ulcers. Following the development of the ulcer, healing is hindered as a result of factors commonly observed in venous ulceration, including venous insufficiency, oedema and impaired angiogenesis. All of these factors are modulated by genetic factors. However, our current understanding of these genetic factors remains limited and does not yet enable us to accurately predict ulceration susceptibility.

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.

Phenotypic characterisation and associations of leg ulcers in adult sickle cell patients

Sickle leg ulcer (SLU) occurs as a result chronic occlusion of the vasculature with consequent necrosis of the skin and subcutaneous tissue usually in proximity of the malleoli. The description of clinical associations and the simultaneous occurrence of SLU and other complications of SCD compared to the non-SLU patients was the aim of this work. A total of 272 (60.8% males and 39.2% females) patients were captured during this time period out of which 68 (51 males and 17 females) had SLU out of whom 20 patients had bilateral leg ulcers. Prevalence of SLU was 25% and the median age of patients was 25 years, frequency of crisis 2 per annum and 44 (74.6%) had been transfused in the past. Median Hb of the group was 7.6 g/dl and 25% had values lower than 6.5. The occurrence of other complications in SLU patients was as follows; 10 had AVN, 9 priapism, 8 had osteomyelitis, 6 nephropathy, stroke 2, osteoarthritis 4 and cholelithiasis 4. There was a significant relationship between the occurrence of SLU and gender of the patient being more in 67males-Likelihood ratio 4.610 (p = 0.032) and the occurrence of pulmonary hypertension-Likelihood ratio 4.762 (p = 0.029). There was no significant association between the occurrence of SLU and other complications of SCD. Leg ulcer patients have a median age of 25 years with a prevalence of 25% but do not necessarily show other features of severe disease phenotypes. SLU patients were more likely to develop pulmonary hypertension. Further studies on impact of environmental factors on the occurrence of SLU are needed to further evaluate its aetiology.

Common, But Neglected: A Comprehensive Review of Leg Ulcers in Sickle Cell Disease

OBJECTIVE

To compile available evidence to better understand the management of leg ulcers in sickle cell disease (SCD), as well as describe potential therapeutic steps that may be required to improve the quality of life of patients with SCD leg ulcers.

DATA SOURCES

MEDLINE, PubMed, EMBASE, and Web of Science databases.

STUDY SELECTION

A comprehensive search was conducted to retrieve relevant studies using the keywords "sickle cell disease and leg ulcer," "ulcer treatments, diagnosis and sickle cell," and "wound sickle cell." Studies published through July 2020 were included.

DATA EXTRACTION

Two independent authors selected all studies that assessed the relationship between leg ulcer and SCD identified from online databases.

DATA SYNTHESIS

The authors have summarized updated information on pathophysiology (vasculopathy linked to chronic hemolysis and endothelial dysfunction), diagnosis, and available treatment options to unravel the dermohematologic connection between leg ulcers and SCD.

CONCLUSIONS

It is the authors' hope that this detailed discussion of the information available on leg ulcers and SCD will lead to a better appreciation of this clinical problem by the clinicians and researchers and in turn have a long-term positive effect on the quality of life of patients with SCD. Researchers should design new trials considering these insights and potential therapeutic approaches based on current knowledge.

Interventions for treating leg ulcers in people with sickle cell disease

BACKGROUND

The frequency of skin ulceration makes an important contributor to the morbidity burden in people with sickle cell disease. Many treatment options are available to the healthcare professional, although it is uncertain which treatments have been assessed for effectiveness in people with sickle cell disease. This is an update of a previously published Cochrane Review.

OBJECTIVES

To assess the clinical effectiveness and harms of interventions for treating leg ulcers in people with sickle cell disease.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register. We searched LILACS (1982 to January 2020), ISI Web of Knowledge (1985 to January 2020), and the Clinical Trials Search Portal of the World Health Organization (January 2020). We checked the reference lists of all the trials identified. We also contacted those groups or individuals who may have completed relevant randomised trials in this area. Date of the last search of the Cochrane Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register: 13 January 2020; date of the last search of the Cochrane Wounds Group Trials Register: 17 February 2017.

SELECTION CRITERIA

Randomised controlled trials of interventions for treating leg ulcers in people with sickle cell disease compared to placebo or an alternative treatment.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies for inclusion. All three authors independently assessed the risk of bias of the included studies and extracted data. We used GRADE to assess the quality of the evidence.

MAIN RESULTS

Six studies met the inclusion criteria (198 participants with 250 ulcers). Each trial investigated a different intervention and within this review we have grouped these as systemic pharmaceutical interventions (L-cartinine, arginine butyrate, isoxsuprine) and topical pharmaceutical interventions (Solcoseryl® cream, arginine-glycine-aspartic acid (RGD) peptide dressing and topical antibiotics). No trials on non-pharmaceutical interventions were included in the review. All trials had an overall unclear or high risk of bias, and drug companies sponsored four of them. We were unable to pool findings due to the heterogeneity in outcome definitions, and inconsistency between the units of randomisation and analysis. Three interventions reported on the change in ulcer size (arginine butyrate, RGD peptide, L-cartinine). Of these, only arginine butyrate showed a reduction of ulcer size compared with a control group, mean reduction -5.10 cm² (95% CI -9.65 to -0.55), but we are uncertain whether this reduces ulcer size compared to standard care alone as the certainty of the evidence has been assessed as very low. Three trials reported on complete leg ulcer closure (isoxsuprine, arginine butyrate, RGD peptide matrix; very low quality of evidence). None reported a clinical benefit. No trial reported on: the time to complete ulcer healing; ulcer-free survival following treatment for sickle cell leg ulcers; quality of life measures; incidence of amputation or harms.

AUTHORS' CONCLUSIONS

Given the very low quality of the evidence identified in this updated Cochrane Review we are uncertain whether any of the assessed pharmaceutical interventions reduce ulcer size or result in leg ulcer closure in treated participants compared to controls. However, this intervention was assessed as having a high risk of bias due to inadequacies in the single trial report. Other included studies were also assessed as having an unclear or high risk of bias. The harm profile of the all interventions remains inconclusive.

Association between inflammatory molecules, nitric oxide metabolites and leg ulcers in individuals with sickle cell anemia

Introduction

Leg ulcers (LUs) are relatively common in patients with sickle cell anemia (SCA). The role of inflammation and nitric oxide (NO) pathways in the pathophysiology of the LU is not understood.

Objective

The aim of this study was to verify the association between inflammatory molecules and nitric oxide metabolites (NOx) and the occurrence of the LU in patients with SCA.

Method

It was a cross-sectional study on adult participants with SCA followed at Fundação Hemominas, a public blood center in Brazil. Eligible participants were recruited and included in one of two groups: Group 1, comprised of cases with SCA (Hb SS) and at least one LU at the time of inclusion in the study and Group 2, comprised of controls with SCA without a history of LU, matched by sex and age to cases. Participants were interviewed to obtain sociodemographic data and blood samples were collected. Clinical and laboratory data were abstracted from medical records. Nitric oxide metabolites (NOx) and inflammatory molecules were quantified using an immunoassay and Multiplex xMAP® technology, respectively. Eighty-seven individuals were included, ranging in age from 17 to 61 years (mean 40 ± 10.7 years); 30 had LU and 57 were controls without LU.

Results

Participants with LU had significantly higher levels of interleukin 8 (IL-8), IL-10, IL-15, NOx and platelet and white blood cell (WBC) counts, when compared to those without LU. Participants with LU had a significantly higher risk of having a history of osteomyelitis and a higher use of antiseptic soap in bathing, when compared to those without LU.

Conclusion

In conclusion, our results showed that NOx, inflammatory molecules and hematological features were associated with LU in Brazilian adults with SCA.