Sickle Cell Anemia Health Article

Definition

Sickle cell anemia, also called sickle cell disease (SS disease), is an inherited condition caused by having abnormal hemoglobin, the protein that carries oxygen in the blood. People with sickle cell anaemia have sickle hemoglobin (HbS) which is different from the normal hemoglobin (HbA).

Description

Children with sickle cell anemia produce two abnormal hemoglobin proteins (inheriting one from each parent), which makes their red blood cells easily destructible while giving them a sickle-like shape. Since the red blood cells do not have a normal shape, their circulation in the small blood vessels is impaired as well as the function of the abnormal hemoglobin (HbS) which can no longer carry oxygen with maximum efficiency.

Transmission

Sickle cell anemia is usually inherited from parents who are carriers, who have the sickle cell trait—a milder form of sickle cell anemia, or one abnormal hemoglobin.

Demographics

Sickle cell anemia and sickle cell trait are found mainly in people whose families come from Africa, the Caribbean, the Eastern Mediterranean, Middle East, and Asia. In the United States, sickle cell anemia affects some 72,000 people. The families of most of the people affected come from Africa. The disease occurs in about one in every 600 African-American births and in one in every 1,000 to 1,400 Hispanic-American births. Some 2 million Americans carry the sickle cell trait and about one in 12 African Americans have the trait.

Causes and symptoms

Sickle cell anemia is caused by an error in the gene that signals the body how to make hemoglobin. The defective gene tells the body to make the abnormal hemoglobin HbS instead of the normal HbA, and this results in deformed red blood cells. The error in the hemoglobin gene is due to a genetic mutation that occurred many thousands of years ago in people living in Africa, the Mediterranean basin, the Middle East, and India. A deadly form of malaria was very common at that time, and research has shown that in areas where malaria was endemic, children who inherited one HbS gene and who, therefore, carried the sickle cell trait, had a survival advantage because, unlike the children who had normal HbA genes, they survived malaria. They grew up, had their own children, and passed on the gene for HbS.

Symptoms or complications associated with sickle cell anemia usually start after the age of four to six months and can include all or some of the following:

• anemia, caused by low amounts of red blood cells in the bloodstream, resulting in insufficient oxygen delivery to tissues and organs
• vaso-occlusive pain, meaning severe episodes of pain in the arms, legs, or back, due to impaired blood circulation in the blood vessels
• chest pain and fever with coughing
• dactylitis, or hand-foot syndrome, with painful swelling of the bones in the hands or feet of young children
• aplastic crises, during which the body stops making new red blood cells causing severe anemia usually following an infection with the parovirus B19, which causes fifth disease
• priapism, a painful and prolonged erection
• stroke, usually causing sudden weakness of one side of the body
• acute splenic sequestration, with pooling of blood causing a sudden enlargement of the spleen
• jaundice, a yellowing of the skin and white of the eyes
• frequent infection with certain bacteria, particularly pneumococcus and salmonella, which are due to auto-infarction of the spleen or death of the spleen due to poor blood flow