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Sickle cell disease is a hereditary hemoglobinopathy caused by a point mutation in the beta-globin gene, resulting in the production of abnormal hemoglobin S (HbS). This autosomal recessive disorder primarily affects individuals of African, Mediterranean, Middle Eastern, and Indian descent. The disease is characterized by chronic hemolytic anemia, vaso-occlusive crises, and progressive organ damage.
The substitution of valine for glutamic acid at position 6 of the beta-globin chain creates hemoglobin S, which polymerizes under deoxygenated conditions, causing red blood cells to assume a rigid, sickle shape. These sickled cells have reduced deformability and increased adhesion to vascular endothelium, leading to vascular occlusion and tissue ischemia. The shortened lifespan of sickled erythrocytes (10-20 days versus normal 120 days) results in chronic hemolytic anemia and compensatory mechanisms including increased cardiac output and bone marrow hyperplasia.
Clinical presentation includes acute painful vaso-occlusive episodes, chronic pain, fatigue from anemia, and complications such as acute chest syndrome, stroke, and organ infarction. Diagnosis is confirmed through hemoglobin electrophoresis or high-performance liquid chromatography showing predominant HbS with absent or reduced HbA. Management focuses on pain control during crises, hydroxyurea therapy to increase fetal hemoglobin production, prophylactic antibiotics, and comprehensive care to prevent and manage complications including regular transfusions when indicated.