Pathophysiology of sickle cell disease: role of cellular and genetic modifiers.

Sickle hemoglobin (HbS), caused by a point mutation in the beta-globin gene of hemoglobin, polymerizes when deoxygenated. The pathophysiology of sickle cell disease results from cellular defects caused directly by the hemoglobin mutation interacting with the environment and many other gene products--a few known, but most yet unidentified--a typical example of epistasis. How normal tissue perfusion is interrupted is complex and why the phenotype of sickle cell disease differs from patient to patient is poorly understood. We review the "classic" aspects of the pathophysiology of sickle cell disease and focus on known and potential modulators of the phenotype of this disorder.