Chronic leg ulcers are a relatively common occurrence in people with homozygous sickle cell disease. Elevated blood viscosity, a classic manifestation of sickle cell disease, may contribute to the formation and reduced healing properties of these chronic ulcers. A July 2013 study published in PLoS showed that patients with sickle cell disease and leg ulcers (n = 24) had 1.9 times higher low-shear blood viscosity and 2.3 times higher high-shear blood viscosity than those with sickle cell disease and without leg ulcers (n = 31). The authors, Bowers et al. suggested that sickle cell-related hyperviscosity "may be linked to a pro-adhesive state in the microcirculation." Elevated blood viscosity along with increased inflammatory markers may have contributed to the pathophysiology of chronic leg ulcers in the subjects, however, tissue oxygenation measured by Visible lightguide spectroscopy was not different between the group with ulcers and the group without ulcers. Despite these findings, the oxygen delivery index, a ratio of hematocrit to viscosity and an indicator of the blood's inherent efficiency of delivery oxygen, was lower in subjects with ulcers than those without ulcers.
Bowers AS, Reid HL, Greenidge A, Landis C, Reid M. Blood viscosity and the expression of inflammatory and adhesion markers in homozygous sickle cell disease subjects with chronic leg ulcers. PLoS One. 2013;8(7):e68929.