Chronic leg ulceration in homozygous sickle cell disease: the role of venous incompetence

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.

Insights into the skin microbiome of sickle cell disease leg ulcers

Leg ulcers are estimated to occur in 1%-10% of North American patients with sickle cell disease (SCD). Their pathophysiology remains poorly defined, but as with other chronic wounds, it is hypothesised that the microbial milieu, or microbiome, contributes to their healing and clinical outcomes. This study utilises 16S ribosomal RNA (rRNA) gene sequencing to describe, for the first time, the microbiome of the SCD leg ulcer and its association with clinical factors. In a cross-sectional analysis of 42 ulcers, we recovered microbial profiles similar to other chronic wounds in the predominance of anaerobic bacteria and opportunistic pathogens including Staphylococcus, Corynebacterium, and Finegoldia. Ulcers separated into two clusters: one defined by predominance of Staphylococcus and smaller surface area, and the other displaying a greater diversity of taxa and larger surface area. We also find that the relative abundance of Porphyromonas is negatively associated with haemoglobin levels, a key clinical severity indicator for SCD, and that Finegoldia relative abundance is negatively associated with CD19+ B cell count. Finally, ratios of Corynebacterium:Lactobacillus and Staphylococcus:Lactobacillus are elevated in the intact skin of individuals with a history of SCD leg ulcers, while the ratio of Lactobacillus:Bacillus is elevated in that of individuals without a history of ulcers. Investigations of the skin microbiome in relation to SCD ulcer pathophysiology can inform clinical guidelines for this poorly understood chronic wound, as well as enhance broader understanding about the role of the skin microbiome in delayed wound healing.

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.

Haematological indices of sickle cell patients with chronic leg ulcers on compression therapy

Background

Recurrent chronic leg ulcers and its are morbidities associated with sickle cell anaemia (SCA). Compression therapy increases the rate of healing of these ulcers and also decreases the rate of recurrence.

Objective

This study evaluated the haematological parameters of patients with SCA and chronic leg ulcers placed on high compression bandaging to provide data for improved ulcer management and prevention.

Methods

Eighteen patients with SCA and chronic leg ulcers were recruited for treatment by compression therapy in Ibadan, Nigeria, from March to June 2015. Eighteen SCA patients with no history of chronic leg ulcers were age and sex matched and recruited as controls. Blood samples, wound biopsies and swabs were collected at different time points for full blood count, microbiology, culture and antimicrobial susceptibility tests. Haemoglobin variants were quantified by high performance liquid chromatography. Fasting blood sugar was tested for leg ulcer patients to determine diabetic status.

Results

Ulcers ranged from 0.5 cm² to 416 cm² (median: 38.4 cm²). Post-intervention ulcer size ranged from 0.0 cm² to 272 cm² (median: 18.6 cm², p < 0.001); four ulcers completely healed. Compared to the control group, haematological indices at commencement of treatment were more severe in leg ulcer patients (p = 0.02). No patients with chronic leg ulcer was diabetic. Microorganisms isolated from the leg ulcers include Pseudomonas aeruginosa, Staphylococcus aureus, Proteus sp., Escherichia coli and Klebsiella oxytoca.

Conclusion

Measures to improve haematological parameters during leg ulcer treatment in SCA patients should be taken to aid wound healing.

Leg Ulcers in Sickle-Cell Disease: Treatment Update

Significance: Sickle-cell leg ulcers (SCLUs) are a severe, chronic, and recurrent complication of sickle-cell disease (SCD). There are no official recommendations for treatment. Recent Advances: Only a few studies with a high level of evidence have been conducted to evaluate treatment of SCLUs. However, several studies have been conducted with a high level of evidence to evaluate the efficacy of treatments in venous leg ulcers, and SCLUs could benefit from these treatments, especially when a venous incompetence or an edema is associated. Pathophysiology of SCLUs includes a vasculopathy related to chronic hemolysis and an endothelial dysfunction, which could be therapeutic approaches to SCLU treatment. Critical Issues: Therapeutic approaches to SCLUs can target SCD on the one hand and skin healing and associated aggravating factors on the other. A review of the literature found only case series and six randomized controlled trials; some offered encouraging results, but most had serious biases. Clinical trials specifically targeting SCLUs are difficult to realize because of the small number of affected patients, in comparison with patients with leg ulcers from other causes. Future Direction: Treating SCLUs remains a challenge. Data in the literature are currently insufficient to offer clear treatment guidelines because of several biases in controlled studies. New studies are under way to assess the efficacy of topical treatments and describe the microbiome of SCLUs. Prevention of SCLU recurrence should be assessed in future clinical trials because the high risk of recurrence is an unsolved critical issue.

A study of the geographic distribution and associated risk factors of leg ulcers within an international cohort of sickle cell disease patients: the CASiRe group analysis

Vasculopathy is a hallmark of sickle cell disease ultimately resulting in chronic end organ damage. Leg ulcer is one of its sequelae, occurring in ~ 5-10% of adult sickle cell patients. The majority of leg ulcer publications to date have emanated from single center cohort studies. As such, there are limited studies on the geographic distribution of leg ulcers and associated risk factors worldwide. The Consortium for the Advancement of Sickle Cell Research (CASiRe) was formed to improve the understanding of the different phenotypes of sickle cell disease patients living in different geographic locations around the world (USA, UK, Italy, Ghana). This cross-sectional cohort sub-study of 659 sickle cell patients aimed to determine the geographic distribution and risk factors associated with leg ulcers. The prevalence of leg ulcers was 10.3% and was associated with older age, SS genotype, male gender, and Ghanaian origin. In fact, the highest prevalence (18.6%) was observed in Ghana. Albuminuria, proteinuria, increased markers of hemolysis (lower hemoglobin, higher total bilirubin), lower oxygen saturation, and lower body mass index were also associated with leg ulceration. Overall, our study identified a predominance of leg ulcers within male hemoglobin SS patients living in sub-Saharan Africa with renal dysfunction and increased hemolysis.

Intima-media thickness of the common femoral artery as a marker of leg ulceration in sickle cell disease patients

Leg ulceration is a debilitating chronic complication of sickle cell disease (SCD) the pathogenesis of which is yet to be fully elucidated. We hypothesized that SCD patients with histories of previous leg ulcers would have intima hyperplasia of the common femoral artery (CFA). We enrolled 44 SCD patients and 33 age-matched and sex-matched controls with hemoglobin AA. Anthropometric measurements, biochemical parameters, and sonographic intima-media thickness (IMT) of the CFA were determined. The median CFA IMT in SCD limbs with history of leg ulcers (SWLU) was 1.0 mm, whereas it was 0.7 mm in SCD limbs with no history of leg ulcer (SNLU) and 0.60 mm in controls (P < .001). Among the SNLU, 70.3% had CFA IMT <0.9 mm, whereas only 29.7% had CFA IMT ≥0.9 mm. Conversely, only 20.8% of SWLU had CFA IMT <0.9 mm, whereas the remaining 79.2% had CFA IMT ≥0.9 mm. All the controls had CFA IMT <0.9 mm. Binary logistic regression to determine the odds of having leg ulcer among SCD limbs with CFA IMT of ≥0.9 mm yielded an odds ratio of 9, indicating that SCD limbs with CFA IMT ≥0.9 mm had a 9 times greater risk of having leg ulcer compared with those with CFA IMT <0.9 mm. There is a significant increase in the CFA IMT of SCD limbs with ulcer compared with controls and SCD limbs without ulcer, suggesting that arterial vasculopathy plays a major role in the formation of these ulcers.

Hematopoietic stem cell transplantation for sickle cell disease: Progress and challenges

Sickle cell disease (SCD) presents challenges to hematopoietic stem cell transplantation (HSCT), including donor availability and morbidity with age/disease severity. However, severe SCD causes irreversible organ damage that HSCT can mitigate. This benefit must be balanced against preparative regimen toxicity, graft-versus-host disease, and mortality risk. We review efforts to balance HSCT complications with the promise of cure, and knowledge gaps that warrant further investigation. We highlight the burden of SCD, HSCT risks and benefits, and SCD families' approach to this balance. We emphasize the necessity for information exchange to ensure a joint decision-making process between providers and patients.

Red blood cell deformability is reduced in homozygous sickle cell disease patients with leg ulcers

Previous reports differ as to whether a decreased elongation index (EI), a proxy for red blood cell (RBC) deformability, is associated with leg ulcers (LU) in people with homozygous sickle cell disease (SCD). We sought to determine whether erythrocyte deformability (ED) and haematological indices were associated with the presence of LU in patients with SCD. The study design was cross-sectional. Twenty-seven patients with LU and 23 with no history of ulceration were recruited into the study. A laser assisted rotational red cell analyzer was used in the determination of the EI. Haematological indices were determined using a CELL-DYN Ruby haematology analyzer. Data were normally distributed and presented as means±SD. Two-sample t-test was used to test for associations between haemorheological variables in SCD patients with and without LU. Statistical significance was taken as p < 0.05. The EI was significantly lower in the group with ulcers (0.30±0.07 vs. 0.35±0.07, p = 0.02). Haematological indices were comparable in patients with and without LU. Erythrocyte deformability, but not haematological indices, was associated with LU in patients with SCD.

Healing of chronic sickle cell disease-associated foot and ankle wounds using transdermal continuous oxygen therapy

OBJECTIVE

Sickle cell disease (SCD) is a complex cause of capillary stasis that can lead to lower extremity venous ulcers. Since SCD is characterised by impaired oxygen delivery that can be exacerbated by lower extremity venous stasis, we sought to determine if direct delivery of oxygen to a lower extremity ulcer associated with SCD could augment healing.

METHOD

We performed a pilot study of a portable device that delivers oxygen directly to the wound site to assess this possibility. The device was assessed in a single patient with three longstanding wounds of the lower extremities associated with SCD: the lateral right ankle, the medial aspect of the distal left leg, and the dorsal left foot. The left leg and left foot wounds received 15 weeks of treatment each.

RESULTS

Both left lower extremity wounds healed, and neither wound has relapsed in the 42 months since the treatment was completed. At 36 months from the completion of treatment, the patient presented to the hospital with renal failure, and with the 27 days of complete bed rest and wound elevation, the right ankle wound shrunk to 55% of the original wound surface area. Transdermal oxygen appears to have assisted in healing and to have provided a sustained benefit that has delayed relapse of the two SCD-associated leg ulcers that received an extended course of treatment. Similarly, complete bed rest appears to aid in the healing of SCD-associated leg ulcers. Further study is needed to determine the mechanism of action and the optimal method of use of the transdermal continuous oxygen delivery device for SCD-associated lower extremity ulcers.

DECLARATION OF INTEREST

No competing financial interests exist for any author. The content of this article was expressly written by the authors listed. No ghostwriters were used to write this article.

A treatment algorithm to identify therapeutic approaches for leg ulcers in patients with sickle cell disease

Sickle cell leg ulcers (SCLUs) are a common complication of sickle cell disease (SCD). Patients who develop ulcers appear to have a more severe haemolysis-associated vasculopathy than individuals who do not develop them, and manifest other complications such as priapism and pulmonary hypertension. SCLUs are slow to heal and often recur, affecting both the emotional and physical well-being of patients. Here we summarise what is known about the pathophysiology of SCLUs, describe available treatment options and propose a treatment algorithm.

Musculoskeletal Manifestations of Sickle Cell Disease: A Review

Sickle cell disease (SCD) is an inherited disorder of abnormal haemoglobin commonly encountered in the West African sub-region. It has varied osteoarticular and non-osseous complications that mimic some surgical conditions. The most common orthopaedic complications include avascular necrosis, osteomyelitis, septic arthritis, etc. A cautious and painstaking evaluation is required in handling these patients. Acute care and anaesthetic precautions are vital in ensuring an uneventful postoperative period.

Interventions for treating leg ulcers in people with sickle cell disease

BACKGROUND

The frequency of skin ulceration makes it 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.

OBJECTIVES

To assess the clinical effectiveness and safety 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 August 2012), the African Index Medicus (up to August 2012), ISI Web of Knowledge (1985 to August 2012), and the Clinical Trials Search Portal of the World Health Organization (August 2012). 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: 21 July 2014; date of the last search of the Cochrane Wounds Group Trials Register: 18 September 2014.

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.

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, RGD peptide dressing, topical antibiotics). Three interventions reported on the change in ulcer size (arginine butyrate, RGD peptide, L-cartinine). Of these, RGD peptide matrix significantly reduced ulcer size compared with a control group, mean reduction 6.60cm(2) (95% CI 5.51 to 7.69; very low quality of evidence). Three trials reported on the incidence of complete closure (isoxsuprine, arginine butyrate, RGD peptide matrix; ranging between low and very low quality of evidence). None reported a significant effect. No trial reported on: the time to complete ulcer healing; ulcer-free survival following treatment for sickle cell leg ulcers; quality of life measures; or incidence of amputation. There was no reported information on the safety of these interventions.

AUTHORS' CONCLUSIONS

There is evidence that a topical intervention (RGD peptide matrix) reduced ulcer size in treated participants compared to controls. This evidence of efficacy is limited by the generally high risk of bias associated with these reports.We planned to analyse results according to general groups: pharmaceutical interventions (systemic and topical); and non-pharmaceutical interventions (surgical and non-surgical). However, we were unable to pool findings due to the heterogeneity in outcome definitions, and inconsistency between the unit of randomisation and the unit of analysis. This heterogeneity, along with a paucity of identified trials, prevented us performing any meta-analyses.This Cochrane review provides some evidence for the effectiveness of one topical intervention - RGD peptide matrix. 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 a high risk of bias. We recommend that readers interpret the trial results with caution. The safety profile of the all interventions was inconclusive.

Haemolysis and abnormal haemorheology in sickle cell anaemia

Although pulmonary hypertension, leg ulcers, priapism, stroke and glomerulopathy in sickle cell anaemia (SCA) result from the adverse effects of chronic haemolysis on vascular function (haemolytic phenotype), osteonecrosis, acute chest syndrome and painful vaso-occlusive crises are caused by abnormal vascular cell adhesion and increased blood viscosity (viscosity-vaso-occlusion phenotype). However, this model with two sub-phenotypes does not take into account the haemorheological dimension. We tested the relationships between the biological parameters reflecting the haemolytic rate (haemolytic component) and red blood cell (RBC) rheological characteristics in 97 adults with SCA. No significant difference in the proportion of patients with low or high haemolytic component in the low and high blood viscosity groups was observed. The RBC elongation index (i.e. deformability) was negatively correlated with the haemolytic component. The RBC aggregates strength (i.e. RBC aggregates robustness) was negatively correlated with RBC elongation index. Sickle RBCs with high density had lower elongation index and higher aggregates strength. In conclusion, (i) the 'haemolytic' phenotype is characterized by decreased RBC deformability and increased RBC aggregates strength and (ii) the viscosity-vaso-occlusive phenotype is characterized by increased RBC deformability but not always by increased blood viscosity. α-thalassaemia modulates the haemorheological properties but other factors seem to be involved.

Clinical findings associated with homozygous sickle cell disease in the Barbadian population--do we need a national SCD registry?

BACKGROUND

Comprehensive care in homozygous sickle cell disease (HbSS) entails universal neonatal screening and subsequent monitoring of identified patients, a process which has been streamlined in the neighbouring island of Jamaica. In preparation for a similar undertaking in Barbados, we have developed a database of persons with known HbSS, and have piloted processes for documenting clinical manifestations. We now present a brief clinical profile of these findings with comparisons to the Jamaican cohort.

METHODS

HbSS participants were recruited from clinics and support groups. A history of select clinical symptoms was taken and blood and urine samples and echocardiograms were analysed. A re-analysis of data from a previous birth cohort was completed.

RESULTS

Forty-eight persons participated (32 F/16 M); age range 10-62 yrs. 94% had a history of ever having a painful crisis. In the past year, 44% of participants had at least one crisis. There were >69 crises in 21 individuals; 61% were self-managed at home and the majority of the others were treated and discharged from hospital; few were admitted. The prevalence of chronic leg ulceration was 27%. Forty-two persons had urinalysis, 44% were diagnosed with albuminuria (urinary protein/creatinine ratio ≥30 mg/g). Thirty-two participants had echocardiography, 28% had a TRJV ≥ 2.5 m/s. Re-analysis of the incidence study revealed a sickle gene frequency (95% CI) of 2.01% (0.24 to 7.21).

CONCLUSION

Although we share a common ancestry, it is thought that HbSS is less common and less severe in Barbados compared to Jamaica. The Jamaican studies reported a sickle gene frequency of 3.15 (2.81 to 3.52); the prevalence of chronic leg ulcers and albuminuria was 29.5% and 42.5% respectively. These comparisons suggest that our initial thoughts may be speculative and that HbSS may be an underestimated clinical problem in Barbados. A prospective neonatal screening programme combined with centralized, routine monitoring of HbSS morbidity and outcomes will definitively answer this question and will improve the evidence-based care and management of HbSS in Barbados.

Interventions for treating leg ulcers in people with sickle cell disease

BACKGROUND

The frequency of skin ulceration makes it 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.

OBJECTIVES

To assess the clinical effectiveness and safety 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 August 2012), the African Index Medicus (up to August 2012), ISI Web of Knowledge (1985 to August 2012), and the Clinical Trials Search Portal of the World Health Organization (August 2012). 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 Group's Haemoglobinopathies Trials Register: 25 May 2012.

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.

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, RGD peptide dressing, topical antibiotics). Three interventions reported on the change in ulcer size (arginine butyrate, RGD peptide, L-cartinine). Of these, RGD peptide matrix significantly reduced ulcer size compared with a control group, mean reduction 6.60cm(2) (95% CI 5.51 to 7.69). Three trials reported on the incidence of complete closure (isoxsuprine, arginine butyrate, RGD peptide matrix). None reported a significant effect. No trial reported on: the time to complete ulcer healing; ulcer-free survival following treatment for sickle cell leg ulcers; quality of life measures; or incidence of amputation. There was no reported information on the safety of these interventions.

AUTHORS' CONCLUSIONS

There is evidence that a topical intervention (RGD peptide matrix) reduced ulcer size in treated participants compared to controls. This evidence of efficacy is limited by the generally high risk of bias associated with these reports.We planned to analyse results according to general groups: pharmaceutical interventions (systemic and topical); and non-pharmaceutical interventions (surgical and non-surgical). However, we were unable to pool findings due to the heterogeneity in outcome definitions, and inconsistency between the unit of randomisation and the unit of analysis. This heterogeneity, along with a paucity of identified trials, prevented us performing any meta-analyses.This Cochrane review provides some evidence for the effectiveness of one topical intervention - RGD peptide matrix. 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 a high risk of bias. We recommend that readers interpret the trial results with caution. The safety profile of the all interventions was inconclusive.

Sickle Cell Disease in the Post Genomic Era: A Monogenic Disease with a Polygenic Phenotype

More than half a century after the discovery of the molecular basis of Sickle Cell Disease (SCD), the causes of the phenotypic heterogeneity of the disease remain unclear. This heterogeneity manifests with different clinical outcomes such as stroke, vaso-occlusive episodes, acute chest syndrome, avascular necrosis, leg ulcers, priapism and retinopathy. These outcomes cannot be explained by the single mutation in the beta-globin gene alone but may be attributed to genetic modifiers and environmental effects. Recent advances in the post human genome sequence era have opened the door for the identification of novel genetic modifiers in SCD. Studies are showing that phenotypes of SCD seem to be modulated by polymorphisms in genes that are involved in inflammation, cell–cell interaction and modulators of oxidant injury and nitric oxide biology. The discovery of genes implicated in different phenotypes will help understanding of the physiopathology of the disease and aid in establishing targeted cures. However, caution is needed in asserting that genetic modifiers are the cause of all SCD phenotypes, because there are other factors such as genetic background of the population, environmental components, socio-economics and psychology that can play significant roles in the clinical heterogeneity.

Hypothetical molecular mechanisms by which local iron overload facilitates the development of venous leg ulcers and multiple sclerosis lesions

This paper presents a hypothetical model of role for iron in the development of venous leg ulcers and multiple sclerosis. Elevated concentrations of iron were found in the skin affected by venous hypertension and also in the areas of brain with multiple sclerosis lesions. Individuals with hemochromatosis gene (HFE) mutations: C282Y and H63D, which result in a less efficient transport of iron by macrophages, are characterized by an increased risk for venous leg ulcer and multiple sclerosis. Multiple sclerosis is a T cell-mediated disease, and T cells probably participate in the development of venous ulcers. This deleterious role of ferric ions could be related to the regulation of T cell proliferation and apoptosis. Under normal conditions excessive accumulation of T cells cannot take place, because nitric oxide and interferon-gamma drive these cells toward apoptosis. However, in tissues with a high concentration of iron, T lymphocytes proliferate instead of undergoing apoptosis. This is possible due to the internalization of the INF-gammaR2 chain of the interferon-gamma receptor, the downregulation of inducible nitric oxide synthase expression in macrophages and the inactivation of the active site of caspases. Yet, it should be emphasized that this hypothesis does not claim for the increased concentration of iron as a direct causal factor for the development of venous ulcerations or multiple sclerosis, but rather, iron is a factor that modulates and exaggerates the autoimmune process. Iron chelators, administered systemically or locally, should potentially exhibit therapeutic and prophylactic activity against venous leg ulcers and multiple sclerosis.

Sickle cell leg ulcers: associations with haemolysis and SNPs in Klotho, TEK and genes of the TGF-beta/BMP pathway

Cutaneous leg ulcers are common in sickle cell anaemia and their risk might be genetically determined. Sickle cell anaemia patients were studied to examine the relationship of leg ulcers with haemolysis and with single nucleotide polymorphisms (SNPs) in candidate genes that could affect sickle vasoocclusion. Leg ulcer patients had lower haemoglobin levels and higher levels of lactate dehydrogenase, bilirubin, aspartate transaminase and reticulocytes than did control patients with sickle cell anaemia but without leg ulcers. Age-adjusted comparisons showed that sickle cell anaemia-alpha thalassaemia was more frequent among controls than cases. These results strongly suggested that the likelihood of having leg ulcers was related to the intensity of haemolysis. 215 SNPs in more than 100 candidate genes were studied. Associations were found with SNPs in Klotho, TEK and several genes in the TGF-beta/BMP signalling pathway by genotypic association analyses. KL directly or indirectly promotes endothelial nitric oxide (NO) production and the TEK receptor tyrosine kinase is involved in angiogenesis. The TGF-beta/BMP signalling pathway modulates wound healing and angiogenesis, among its other functions. Haemolysis-driven phenotypes, such as leg ulcers, could be improved by agents that reduce sickle erythrocyte density or increase NO bioavailability.

Leg Ulceration in Sickle Cell Disease: Medieval Medicine in a Modern World

Leg ulceration is now recognized as an important complication of sickle cell disease, especially of the SS genotype. Since there is no convincing evidence of delayed healing of operation scars or of wounds elsewhere in the body, it must be concluded that factors specific to the lower leg render patients prone to delayed healing at this site. Many lesions are traumatic in origin and since there is considerable variation in healing rates among the normal population, it is useful to define chronic leg ulceration on the basis of a minimal duration, which in Jamaican studies has required at least 3 months and sometimes 6 months before healing. This minimal duration avoids the difficulties of interpreting the significance of briefer lesions since the moment of final healing may be poorly defined (patients may conclude that a scab represents healing whereas small lesions persist beneath) and often goes undocumented as patients may not report and medical attendants may not enquire, the date of final healing.

Are there clinical phenotypes of homozygous sickle cell disease?

The distribution of clinical features was examined in subjects with homozygous sickle cell (SS) disease in the Jamaican Cohort Study to determine whether there is evidence of distinct clustering of symptoms or clinical phenotypes. A twofold model yielded groups that could be interpreted as painful crisis or leg ulcer phenotypes and 78% of patients were classified with 95% confidence into one of these. The painful crisis phenotype also manifested higher frequencies of dactylitis, meningitis/septicaemia, acute chest syndrome and stroke. Attempts to define a three-group model were less convincing although 43% of patients could be allocated with 95% confidence. The three-group model essentially divided subjects with the leg ulcer phenotype into subgroups with higher and lower frequencies of painful crisis, dactylitis, meningitis/septicaemia and acute chest syndrome. In the three-group model, the painful crisis phenotype had lower total haemoglobin, fetal haemoglobin, mean cell volume and higher reticulocytes but there was no apparent influence of alpha thalassaemia or beta globin haplotype. Both environmental and genetic factors are likely to contribute to most manifestations of SS disease and the evidence for different clinical phenotypes suggests that a search for associated genetic polymorphisms may provide insights into the mechanisms of clinical variability in SS disease.