Description Medical Red Blood Cell Disorders Age 17

Sickle cell disease is a genetic, autosomal recessive disorder that results in abnormalities of the globin genes of the hemoglobin molecule of the red blood cells (RBCs). It is more common in African Americans than in other groups in the United States. It can be in the form of sickle cell anemia or either sickle cell thalassemia or sickle cell hemoglobin (Hb) C. Sickle cell anemia, the severest of the sickle cell disorders, is homozygous and has no known cure. Sickle cell trait occurs when a child inherits normal Hb from one parent and Hb S (the abnormal Hb) from the other; people with the sickle cell trait are carriers only and rarely manifest the clinical signs of the disorder.

The RBCs that contain more Hb S than Hb A are prone to sickling when they are exposed to decreased oxygen tension in the blood. The cells become more elongated, thus the term "sickle." Once sickled, RBCs are more rigid, fragile, and rapidly destroyed. The RBCs therefore have a short survival time (30 to 40 days, as compared with a normal 120-day survival rate), a decreased oxygen-carrying capacity, and low Hb content. They cannot flow easily through tiny capillary beds and may become clumped and cause obstructions. The obstructions can lead to ischemia and necrosis, which produce the major clinical manifestations of pain. In people with sickle cell disease, approximately 50% do not survive beyond age 20 years, and most people do not live past 50 years of age. Complications include chronic obstructive pulmonary disease, congestive heart failure, and infarction of organs such as the spleen, retina, kidneys, and even the brain.

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