BackgroundLittle is known about the effects of blood rheology on the occurrence of acute chest syndrome and painful vaso-occlusive crises in children with sickle cell anemia and hemoglobin SC disease. Design and MethodsTo address this issue, steady-state hemorheological profiles (blood viscosity, red blood cell deformability, aggregation properties) and hematologic parameters were assessed in 44 children with sickle cell anemia and 49 children with hemoglobin SC disease (8-16 years old) followed since birth. Clinical charts were retrospectively reviewed to determine prior acute chest syndrome or vaso-occlusive episodes, and rates of these complications were calculated. ResultsMultivariate analysis revealed that: 1) a higher steady-state blood viscosity was associated with a higher rate of vaso-occlusive crises in children with sickle cell anemia, but not in children with hemoglobin SC disease; 2) a higher steady-state red blood cell disaggregation threshold was associated with previous history of acute chest syndrome in children with hemoglobin SC disease and boys with sickle cell anemia. ConclusionsOur results indicate for the first time that the red blood cell aggregation properties may play a role in the pathophysiology of acute chest syndrome in children with hemoglobin SC disease and boys with sickle cell anemia. In addition, whereas greater blood viscosity is associated with a higher rate of vaso-occlusive crises in children with sickle cell anemia, no association was found in children with hemoglobin SC disease, underscoring differences in the etiology of vaso-occlusive crises between sickle cell anemia and hemoglobin SC disease.

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Leg ulcer is a disabling complication in patients with sickle cell anemia (SCA) but the exact pathophysiological mechanisms are unknown. The aim of this study was to identify the hematological and hemorheological alterations associated with recurrent leg ulcers. Sixty-two SCA patients who never experienced leg ulcers (ULC-) and 13 SCA patients with a positive history of recurrent leg ulcers (ULC+) - but with no leg ulcers at the time of the study – were recruited. All patients were in steady state condition. Blood was sampled to perform hematological, biochemical (hemolytic markers) and hemorheological analyses (blood viscosity, red blood cell deformability and aggregation properties). The hematocrit-to-viscosity ratio (HVR), which reflects the red blood cell oxygen transport efficiency, was calculated for each subject. Patients from the ULC+ group were older than patients from the ULC- group. Anemia (red blood cell count, hematocrit and hemoglobin levels) was more pronounced in the ULC+ group. Lactate dehydrogenase level was higher in the ULC+ group than in the ULC- group. Neither blood viscosity, nor RBC aggregation properties differed between the two groups. HVR was lower and RBC deformability tended to be reduced in the ULC+ group. Our study confirmed increased hemolytic rate and anemia in SCA patients with leg ulcers recurrence. Furthermore, our data suggest that although systemic blood viscosity is not a major factor involved in the pathophysiology of this complication, decreased red blood cell oxygen transport efficiency (i.e., low hematocrit/viscosity ratio) may play a role.

We analyzed the records of 153 Guadeloupean children with sickle cell anemia (SCA), for whom clinical and laboratory data were prospectively collected (mean follow-up duration 8.4 +/- 4.6 yr). Prevalence and age-specific frequencies of acute clinical events were determined and correlations between complications, hematological parameters and potential modulating factors investigated. Painful crisis and acute chest syndrome (ACS) were the two most common complications, affecting 65.4% and 58.8% of the patients, respectively. The frequency of acute anemia was 49.7% (acute splenic sequestration 24.8%; acute aplastic anemia 15.0%). Prevalences of septicemia-meningitis and osteomyelitis were 15.7% and 16.3%, respectively. A higher incidence of infections, painful crises and acute anemia was detected in patients who developed ACS. The well-documented protective effect of HbF level on the overall disease expression was observed with higher HbF level in asymptomatic than in symptomatic patients (17.5% +/- 8% vs. 9.9% +/- 6.4%, P = 0.01) with similar ages and sex ratio. It was also confirmed on ACS and, for the first time, further extended to acute anemic events and septicemia. Besides its effect on hematological parameters, alpha-thalassemia seems to have little impact on the prevalence of complications, as do beta(S)-globin haplotypes. Comparison with other series suggests that the natural history of SCA in Guadeloupe is more similar to that in Jamaica with regard to those reported in Europe and the United States, suggesting a potential impact of environmental factors on the clinical course of the disease.