Cumming et al, in The Jamaican Cohort Study, reported that high serum LDH, with low socio-economic status and venous incompetence, were strong predictors of chronic leg ulceration in SCA patients. Similar observation was made by Taylor et al who observed higher frequency of patients with a positive history of leg ulcers in the top quartile of serum LDH level in the NIH database and the Cooperative Study of Sickle Cell Disease database (CSSD). Nolan et al shown that patients with sickle cell anemia (SCA) and leg ulcers had lower hemoglobin level and higher levels of lactate dehydrogenase (LDH), bilirubin, aspartate transaminase and reticulocyte counts than SCA patients without leg ulcers.
While the exact causes of recurrent leg ulcers are unknown, several studies support a role of hemolysis. Leg ulcers are often refractory to treatment and are prone to recurrence. Leg ulcers have been previously reported in 25-65% of adult sickle cell patients in Jamaica but the incidence is much lower (2-2.5%) in North America. 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. Our study confirmed increased hemolytic rate and anemia in SCA patients with leg ulcers recurrence. HVR was lower and RBC deformability tended to be reduced in the ULC+ group. Neither blood viscosity, nor RBC aggregation properties differed between the two groups. Lactate dehydrogenase level was higher in the ULC+ group than in the ULC- group. Anemia (red blood cell count, hematocrit and hemoglobin levels) was more pronounced in the ULC+ group. Patients from the ULC+ group were older than patients from the ULC- group. The hematocrit-to-viscosity ratio (HVR), which reflects the red blood cell oxygen transport efficiency, was calculated for each subject. Blood was sampled to perform hematological, biochemical (hemolytic markers) and hemorheological analyses (blood viscosity, red blood cell deformability and aggregation properties). All patients were in steady state condition. 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. The aim of this study was to identify the hematological and hemorheological alterations associated with recurrent leg ulcers. Leg ulcer is a disabling complication in patients with sickle cell anemia (SCA) but the exact pathophysiological mechanisms are unknown.
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