Sickle cell anemia is a type of anemia named after a characteristic change in shape that occurs in the red blood cells Figure 01. Anemia is a condition in which people do not have enough red blood cells. Red blood cells carry oxygen to body tissues with the help of a protein called hemoglobin. Normal red blood cells are circular, like a doughnut, and flexible. The cells of patients with sickle cell anemia have high levels of an abnormal type of hemoglobin called hemoglobin S. Hemoglobin S causes red blood cells to stiffen into a sickle shape, which looks like a crescent moon. Sickled cells die in about 10 to 20 days, compared to 120 days for normal red blood cells. Anemia develops because the body can't replace the dying cells fast enough.
Sickle cell anemia is an inherited disease. To develop sickle cell anemia, a person must receive sickle cell genes from both parents. People who inherit a sickle cell gene from one parent and a normal gene from the other will have sickle cell trait. People with sickle cell trait generally do not have symptoms, but can pass the defective gene on to offspring. If each parent has a sickle cell gene, their children have a 25% chance of having sickle cell anemia and a 50% chance of having sickle cell trait.
Millions of people worldwide suffer from sickle cell anemia; in the US, about 72,000 people have sickle cell anemia, and about 2 million have sickle cell trait.
A sickle cell crisis is an episode of pain that occurs when cells do not get needed oxygen. Patients with sickle cell anemia do not have enough red blood cells to carry sufficient amounts of oxygen to the body. Sickle cell crises are characterized by severe pain, and frequently require medical treatment. Patients with sickle cell trait do not usually develop sickle cell crisis. However, they may first become aware that they are carriers if they develop stress or another illness that is accompanied by pain severe enough to require a doctor's attention.
Figure 01. Sickled Cells
Sickle cell anemia is an inherited genetic disease, requiring a sickle cell gene from each parent. If both parents carry a defective gene for sickle cell anemia, each child they produce has a 25% chance of having the disease and a 50% chance of having sickle cell gene, or trait. People with sickle cell trait have only one sickle cell gene, and usually do not have symptoms. However, they can pass the trait to their children. Some patients inherit one sickle cell gene and another abnormal hemoglobin gene. These people may have symptoms similar to those who inherited two sickle cell genes.
Dehydration, cold temperatures, infections, low oxygen levels, excessive alcohol intake, stress, and pregnancy may lead to a sickle cell crisis.
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