Extracorpuscular factors in the pathogenesis of sickle cell disease.

Sickle erythrocytes adhere abnormally to human vascular endothelial cells. The propensity for endothelial adherence varies among individuals with sickle cell disease and correlates significantly with their clinical vasocclusive severity. Sickle erythrocytes adhere more avidly to injured endothelium, under hyperosmolar conditions, and in the presence of increased fibrinogen concentrations. Thus, alterations in the erythrocyte's environment might predispose towards vasocclusion by enhancing erythrocyte/endothelial interactions, perhaps explaining the association between concurrent illness and the development of pain crisis in sickle cell disease.