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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 involves the red blood cells, or hemoglobin, and their ability to carry oxygen. Normal hemoglobin cells are smooth, round, and flexible, like the letter "O," so they can move through the vessels in our bodies easily. Sickle cell hemoglobin cells are stiff and sticky, and form into the shape of a sickle, or 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 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 hemoglobin 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 hemoglobin 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 are:

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, Native American, and Mediterranean heritage.

It has been estimated that over 72,000 people in the US are affected by the disease. 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 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 (HbSS) 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. 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

Children with sickle cell disease = S S (one in four, or 25 percent)

Children who are carriers of the gene like their parents = A S S A
(two in four, or 50 percent have sickle cell trait)

Children who do not get the gene from either parent: A A (one in four, or 25 percent)

Once parents have had a child with sickle cell disease, there is a one in four, or 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 75 percent chance, for another child to 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. Each child may experience symptoms differently. Symptoms and complications may include, but are not limited to, the following:

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

How is sickle cell disease diagnosed?

In addition to a complete medical history and physical examination, diagnostic procedures for sickle cell may include additional blood tests, a complete family history, and results of newborn screening.

Many states now perform hemoglobinopathy testing (testing babies for abnormalities of hemoglobin) as part of the newborn screening blood tests that are routinely done. "State newborn screening" refers to a test done on every baby born in every state of the country within the first few days of life, to detect serious, life-threatening diseases. State laws require that babies be tested between 2 and 7 days of age, even if the baby seems healthy and has no symptoms of health problems.

Early diagnosis is essential in providing proper preventative treatment for some of the devastating complications of the disease.

A hemoglobin electrophoresis is a blood test that can determine if the child 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 and its complications will be determined by your child's physician based on:

Early diagnosis and prevention of complications is critical in sickle cell disease treatment.

Treatment options may include, but are not limited to, the following:

Long-term outlook for a child with sickle cell disease:

Several factors predict the long term survival of a child with this disease including the following:

The life expectancy has increased over the past 30 years and many individuals suffering with sickle cell disease can now live into their mid-40s and beyond. Advances in preventative care and new medications have reduced the life-threatening complications of sickle cell. However, it is still a severe, chronic, and sometimes fatal disease.

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Online Resources of Hematology & Blood Disorders


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