Venous insufficiency is not the cause of leg ulcers in sickle cell disease

Abnormal Lower Extremity Hemodynamics at Doppler US in Children with Sickle Cell Anemia

Background Children with sickle cell anemia (SCA) are predisposed to developing leg ulcers in early adolescence; however, the underlying physiologic mechanisms are not well understood, which hinders the development of prophylactic antiulcer interventions. Purpose To determine if occlusive arterial disease or abnormal hemodynamics exist in the lower limb peripheral arteries of children with SCA. Materials and Methods This was a prospective cross-sectional study conducted between July 2020 and May 2021. Two groups of participants were enrolled: children with SCA and healthy controls. Each child had their anthropometric measurements taken, followed by B-mode, color Doppler, and spectral Doppler US evaluation of the distal anterior and posterior tibial arteries. Ankle-brachial index evaluation was also performed. Hemodynamic values were compared between children with SCA and healthy controls, with statistical significance set at the P < .05 level. Results Forty-five children with SCA (mean age, 9.5 years ± 3.7 [SD]; 26 boys) and 45 healthy controls (mean age, 9.3 years ± 3.8; 25 boys) were evaluated. Children with SCA had higher peak systolic velocities, end-diastolic velocities, and blood volume flow in their distal anterior and posterior tibial arteries compared with the healthy participants (P < .001 across all 12 measurements). Children with SCA also had lower resistive index and pulsatility index values compared with healthy controls in at least one of the anterior and posterior tibial arteries bilaterally. Monophasic spectral patterns were exclusively observed in participants with SCA. The ankle-brachial index values for the participants with SCA (mean, 1.09 ± 0.08) and healthy participants (mean, 1.06 ± 0.02) were within normal range. Conclusion Abnormal peripheral hemodynamic characteristics were found in the lower limbs of children with sickle cell anemia. No evidence of occlusive peripheral artery disease was present. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Paltiel in this issue.

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.

Vasculopathy, inflammation, and blood flow in leg ulcers of patients with sickle cell anemia

Chronic leg ulcers are frequent and debilitating complications of sickle cell anemia. Inadequate blood supply has been postulated to be an important factor in their occurrence and delayed healing. Little is known about their microcirculatory and histopathological changes. We evaluated the microcirculation of lower extremity ulcers with laser speckle contrast imaging and infrared thermography and obtained clinical and laboratory characteristics in 18 adults with sickle cell anemia and chronic leg ulcers. Skin biopsies were obtained in four subjects. Subjects had markers of severe disease, anemia, high degree of hemolysis, inflammation, and thrombophilia. The highest blood flow was present in the ulcer bed, progressively less in the immediate periwound area, and an unaffected control skin area in the same extremity. Microscopic examination showed evidence of venostasis, inflammation, and vasculopathy. Blood vessels were increased in number, had activated endothelium and evidence of thrombosis/recanalization. High blood flow may be due to chronic inflammation, cutaneous vasodilatation, venostasis, and in situ thrombosis. These changes in skin microcirculation are similar to chronic venous ulcers in the non-sickle cell disease (SCD) population, thus suggesting that leg ulcers may be another end-organ complication with endothelial dysfunction that appears in patients with SCD at a younger age and with higher frequency than in the general population.

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.

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

Chronic leg ulceration is a common cause of morbidity in Jamaican patients with homozygous sickle cell (SS) disease. Ulcers heal more rapidly on bed rest and deteriorate on prolonged standing, suggesting a role of venous hypertension in their persistence. This hypothesis has been tested by Doppler detection of venous competence in SS patients and in matched controls with a normal haemoglobin (AA) genotype in the Jamaican Cohort Study. Venous incompetence was significantly more frequent in SS disease [137/183 (75%)] than in non-pregnant AA controls [53/137 (39%)]. Past or present ulceration occurred in 78 (43%) SS patients, with a highly significant association between leg ulceration and venous incompetence in the same leg (P < 0.001). Prominence and/or varicosities of the veins and spontaneous leg ulcers were more common among patients with multiple sites of incompetence. The association of venous incompetence with chronic leg ulceration identifies a further pathological mechanism contributing to the morbidity of SS disease. The cause of venous incompetence is unknown but the sluggish circulation associated with dependency, turbidity and impaired linear flow at venous valves, hypoxia-induced sickling, the rheological effects of high white cell counts, and activation of components of the coagulation system may all contribute. Venous hypertension in SS patients with leg ulceration suggests that firm elastic supportive dressings might promote healing of chronic leg ulcers.

Leg ulceration in the sickle cell patient

BACKGROUND

The purpose of this study was to determine cost of care for leg ulcers in sickle cell patients and suggest an improved modality in ulcer care.

STUDY DESIGN

We performed a retrospective study of a group of sickle cell disease patients with leg ulcers.

RESULTS

Eighteen patients with a leg ulcer (duration: mean, 53.7 months), sickle cell disease, and a mean of 20.7 years of age had various modalities of treatment with the only consistency in healing being a commercial moist-wound dressing.

CONCLUSIONS

There is no consistency in the treatment of the sickle cell patient with a leg ulcer. Treatment with a moist dressing had the best results.

Leg ulcers in sickle cell disease

Leg ulcers are a frequent complication in patients with sickle cell anemia and S/beta thalassemia causing significant physical disability and negative psychologic and social impact. Systematic conservative approaches to treatment using gentle debridement and control of edema result in rapid healing of most ulcers. Chronic recalcitrant ulcers are a challenge to the clinician and patient. Controlled clinical trials are not available to fully define the therapeutic approach to the chronic leg ulcers.