Robert Wood Johnson University Hospital
 

Sickle Cell Disease

Sickle Cell Disease

What is sickle cell disease?

Sickle cell disease is an inherited blood disorder characterized by defective hemoglobin (a protein in red blood cells that carries oxygen to the tissues of the body).

Sickle cell disease inhibits the ability of hemogloblin in red blood cells to carry oxygen. Cells containing normal hemoglobin are smooth, disk-shaped, and flexible, like doughnuts without holes, so they can move through the vessels in our bodies easily. Cells containing sickle cell hemoglobin are stiff and sticky, and form into the shape of a sickle or crescent, like the letter C, when they lose their oxygen. These sickle cells tend to cluster together, and cannot easily move through the blood vessels. The cluster causes a blockage in small arteries or capillaries and stops the movement of healthy, normal oxygen-carrying blood. This blockage is what causes the painful and damaging complications of sickle cell disease.

Sickle cells only live for about 10 to 20 days, while normal red blood cells can live up to 120 days. Also, sickle cells risk being destroyed by the spleen because of their shape and stiffness. The spleen is an organ that helps filter the blood of infections and sickled cells get stuck in this filter and die. Due to the decreased number of healthy red blood cells circulating in the body, a person with sickle cell disease is chronically anemic. The spleen also suffers damage from the sickled cells blocking healthy oxygen carrying cells. Without a normal functioning spleen, these individuals are more at risk for infections. Infants and young children are at risk for life-threatening infections.

The most common variations of the sickle cell gene include the following:

All forms of sickle cell disease can exhibit the complications associated with the disease.

Who is affected by sickle cell disease?

Sickle cell disease primarily affects those of African descent and Hispanics of Caribbean ancestry, but the trait has also been found in those with Middle Eastern, Indian, Latin American, American Indians, and Mediterranean heritage.

It has been estimated that over 70,000 people in the U.S. are affected by sickle cell anemia and that 2 million people have sickle cell trait. Approximately one in 12 African-Americans has sickle cell trait. Millions worldwide suffer complications from sickle cell disease.

What causes sickle cell disease?

Sickle cell is an inherited disease caused by a genetic mutation. Genes are found on structures in the cells of our body called chromosomes. There are normally 46 total, or 23 pairs, of chromosomes in each cell of our body. The 11th pair of chromosomes contains a gene responsible for normal hemoglobin production.

A mutation or error in this gene is what causes sickle cell disease. This mutation is thought to have originated in areas of the world where malaria was common, since people with sickle trait do not get as sick when they get malaria. The sickle trait actually protects them from the parasite that causes malaria, which is carried by mosquitoes. Malaria is most often seen in Africa and in the Mediterranean area of Europe.

Sickle cell is a genetic disease. A person will be born with sickle cell disease only if two HbS genes are inherited—one from the mother and one from the father. A person who has only one HbS gene is healthy and said to be a "carrier" of the disease. They may also be described as having sickle cell trait. A carrier has an increased chance to have a child with sickle cell disease if he or she has a child with someone who also has a sickle cell gene. This type of inheritance is called autosomal recessive.

Autosomal means that the gene is on one of the first 22 pairs of chromosomes that do not determine gender, so that males and females are equally affected by the disease.

Recessive means that two copies of the gene, one inherited from each parent, are necessary to have the condition.

Genetic illustration, two parents with sickle cell trait
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In this couple, there is a risk of having:

For parents who are each carriers of a sickle cell gene, there is a one in four, or a 25 percent chance with each subsequent pregnancy, for another child to be born with sickle cell disease. This means that there is a three out of four, or a 75 percent chance, that another child will not have sickle cell disease. There is a 50 percent chance that a child will be born with sickle cell trait, like the parents.

What are the symptoms of sickle cell disease?

The following is a list of symptoms and complications associated with sickle cell disease. However, each individual may experience symptoms differently. Symptoms and complications may include, but are not limited to, the following:

Any and all major organs are affected by sickle cell disease. The liver, heart, kidneys, gallbladder, eyes, bones, and joints can suffer damage from the abnormal function of the sickle cells and their inability to flow through the small blood vessels correctly. Problems may include the following:

The symptoms of sickle cell disease may resemble other blood disorders or medical problems. Always consult your doctor for a diagnosis.

How is sickle cell disease diagnosed?

In addition to a complete medical history and physical examination, diagnostic procedures for sickle cell disease may include blood tests and other evaluation procedures. Many states provide routine newborn screening blood tests in order to begin proper treatment as soon as possible. Early diagnosis is essential in providing proper preventative treatment for some of the devastating complications of the disease.

Hemoglobin electrophoresis is a blood test that can determine if a person is a carrier of a specific sickle cell trait, or has any of the diseases associated with the sickle cell gene.

Treatment for sickle cell disease

Specific treatment for sickle cell disease will be determined by your doctor based on:

Early diagnosis and prevention of complications is critical in sickle cell disease treatment. The objectives of treatment are to prevent organ damage including strokes, prevent infection, and treat symptoms. Treatment may include:

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