Sickle-Cell Anemia

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Sickle-Cell Anemia, genetic disorder of the blood leading to frequent and severe infections, damage to major organs, and episodes of unpredictable pain in the back, chest, abdomen, and extremities. Early symptoms appear at about six months of age and may include serious infections, pain and swelling in the hands and feet, and enlargement of the abdomen and heart.

Sickle-cell anemia is caused by a defective gene that produces an abnormal form of hemoglobin, the component of red blood cells responsible for transporting oxygen from the lungs to the tissues. The abnormal hemoglobin, called hemoglobin S, distorts red blood cells after they release oxygen in the tissues. These distorted cells are called sickled cells because of their resemblance to the sickle, a type of crescent-shaped cutting blade used in agriculture. The sickled shape makes it difficult for these cells to pass through tiny blood vessels, resulting in intensely painful blockages that prevent vital oxygen and nutrients in the blood from reaching organs and tissues, impairing their function. As a result, sickle-cell patients are also vulnerable to a number of infections. When the blood flow to the brain is affected, sickle-cell patients may experience brain damage, such as stroke. Sickle cells also break apart more readily than healthy red blood cells, leading to a deficiency of red blood cells, known as anemia.

Sickle-cell anemia is an autosomal recessive genetic disease—that is, a child with the disease must inherit one copy of the defective hemoglobin gene from each parent. Many people carry one hemoglobin S gene with no significant health problems as a result. But these carriers of the sickle-cell gene can pass the gene to their children. When both parents are carriers, they have a one in four chance with every pregnancy of having a child with sickle-cell anemia.

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