blood disorders
Sickle Cell Disease
Introduction
Sickle cell disease is an inherited genetic abnormality of hemoglobin (the oxygen-carrying protein found in red blood cells) characterized by sickle (crescent)-shaped red blood cells and chronic anemia caused by excessive destruction of the abnormal red blood cells. People always have anemia and sometimes jaundice. Worsening anemia, fever, and shortness of breath with pain in the long bones, abdomen, and chest can indicate sickle cell crisis. A special blood test called electrophoresis can be used to determine whether people have sickle cell disease. Avoiding activities that may cause crises and treating infections and other disorders quickly can help prevent crises. (See also Overview of Anemia .) Sickle cell disease affects people with African or Black American ancestry almost exclusively. About 10% of people with such ancestry in the United States have one copy of the gene for sickle cell disease (that is, they have sickle cell trait). People who have sickle cell trait do not develop sickle cell disease, but they do have increased risks of some complications such as blood in their urine. About 0.3% of people with African or Black American ancestry have two copies of the gene. These people develop the disease. Normal red blood cells are flexible and disk-shaped, thicker at the edges than in the middle. In several hereditary disorders, red blood cells become spherical (in hereditary spherocytosis), oval (in hereditary elliptocytosis), or sickle-shaped (in sickle cell disease). In sickle cell disease, the red blood cells contain an abnormal form of hemoglobin (the protein that carries oxygen). The abnormal form of hemoglobin is called hemoglobin S. When red blood cells contain a large amount of hemoglobin S, they can become deformed into a sickle shape and less flexible. Not every red blood cell is sickle-shaped. The sickle-shaped cells become more numerous when people have infections or low levels of oxygen in the blood. The sickle cells are fragile and break apart easily. Because the sickle cells are stiff, they have difficulty traveling through the smallest blood vessels (capillaries), blocking blood flow and reducing oxygen supply to tissues in areas where capillaries are blocked. The blockage of blood flow can cause pain and, over time, cause damage to the spleen, kidneys, brain, bones, and other organs. Chronic Kidney Disease and 