Sickle Cell

Sickle cell anaemia is a severe hereditary form of anaemia in which a mutated form of hemoglobin distorts the red blood cells into a crescent shape at low oxygen levels. It is most common among those of African descent.

Sickle cell anemia (sickle cell disease) is a disorder of the blood caused by an inherited abnormal hemoglobin (the oxygen-carrying protein within the red blood cells). The abnormal hemoglobin causes distorted (sickled) red blood cells. The sickled red blood cells are fragile and prone to rupture. When the number of red blood cells decreases from rupture (hemolysis), anemia is the result. This condition is referred to as sickle cell anemia. The irregular sickled cells also block blood vessels causing tissue and organ damage, and pain.

Sickle cell anemia is one of the most common inherited blood anemias. The disease primarily affects Africans and African Americans. It is estimated that in the United States, some 90,000 to 100,000 Americans are afflicted with sickle cell anemia. Overall, current estimates are that one in 500 U.S. African American births is affected with sickle cell anemia.

There are various types of sickle cell anaemia. Hemoglobin is the protein in red blood cells that carries oxygen. It normally has two alpha chains and two beta chains. The four main types of sickle cell anemia are caused by different mutations in these genes.

Hemoglobin SS disease: Hemoglobin SS disease is the most common type of sickle cell disease. It occurs when one inherits copies of the hemoglobin S gene from both parents. This forms hemoglobin known as Hb SS. As the most severe form of SCD, individuals with this form also experience the worst symptoms at a higher rate.

Hemoglobin SC disease: Hemoglobin SC disease is the second most common type of sickle cell disease. It occurs when one inherits the Hb C gene from one parent and the Hb S gene from the other. Individuals with Hb SC have similar symptoms to individuals with Hb SS. However, the anemia is less severe.

Hemoglobin SB+ (beta) thalassemia: Hemoglobin SB+ (beta) thalassemia affects beta globin gene production. The size of the red blood cell is reduced because less beta protein is made. If inherited with the Hb S gene, you will have hemoglobin S beta thalassemia. Symptoms are not as severe.

Hemoglobin SB 0 (Beta-zero) thalassemia: Sickle beta-zero thalassemia is the fourth type of sickle cell disease. It also involves the beta globin gene. It has similar symptoms to Hb SS anemia. However, sometimes the symptoms of beta zero thalassemia are more severe. It is associated with a poorer prognosis.

Hemoglobin SD, hemoglobin SE, and hemoglobin SO: These types of sickle cell disease are rarer and usually don’t have severe symptoms.

Sickle cell trait: People who only inherit a mutated gene (hemoglobin S) from one parent are said to have sickle cell trait. They may have no symptoms or reduced symptoms.

Sickle cell anemia is caused by a mutation in the gene that tells your body to make the red, iron-rich compound that gives blood its red color (hemoglobin). Hemoglobin allows red blood cells to carry oxygen from your lungs to all parts of your body. In sickle cell anemia, the abnormal hemoglobin causes red blood cells to become rigid, sticky and misshapen.

The sickle cell gene is passed from generation to generation in a pattern of inheritance called autosomal recessive inheritance. This means that both the mother and the father must pass on the defective form of the gene for a child to be affected.

If only one parent passes the sickle cell gene to the child, that child will have the sickle cell trait. With one normal hemoglobin gene and one defective form of the gene, people with the sickle cell trait make both normal hemoglobin and sickle cell hemoglobin. Their blood might contain some sickle cells, but they generally don't have symptoms. But they are carriers of the disease, which means they can pass the gene to their children.

Tests to detect sickle cell genes before birth-Sickle cell disease can be diagnosed in an unborn baby by sampling some of the fluid surrounding the baby in the mother's womb (amniotic fluid) to look for the sickle cell gene. Bone marrow transplant, also known as stem cell transplant, offers the only potential cure for sickle cell anemia. It's usually reserved for people younger than age 16 because the risks increase for people older than 16. Finding a donor is difficult, and the procedure has serious risks associated with it, including death.

Treatments might include medications to reduce pain and prevent complications, and blood transfusions, as well as a bone marrow transplant.

Blood transfusions: In a red blood cell transfusion, red blood cells are removed from a supply of donated blood, then given intravenously to a person with sickle cell anemia.

Blood transfusions increase the number of normal red blood cells in circulation, helping to relieve anemia. In children with sickle cell anemia at high risk of stroke, regular blood transfusions can decrease the risk. Transfusions can also be used to treat other complications of sickle cell anemia, or they can be given to prevent complications.

Blood transfusions carry some risk, including infection and excess iron buildup in your body. Because excess iron can damage your heart, liver and other organs, people who undergo regular transfusions might need treatment to reduce iron levels.

Bone marrow transplant: A bone marrow transplant also called a stem cell transplant, involves replacing bone marrow affected by sickle cell anemia with healthy bone marrow from a donor. The procedure usually uses a matched donor, such as a sibling, who doesn't have sickle cell anemia. For many, donors aren't available. But stem cells from umbilical cord blood might be an option.

Because of the risks associated with a bone marrow transplant, the procedure is recommended only for people, usually children, who have significant symptoms and problems from sickle cell anemia.

Treating sickle cell complications: Doctors treat most complications of sickle cell anemia as they occur. Treatment might include antibiotics, vitamins, blood transfusions, pain-relieving medicines, other medications and possibly surgery, such as to correct vision problems or to remove a damaged spleen.

Scientists are studying new treatments for sickle cell anemia, including:

• Gene therapy: Researchers are exploring whether inserting a normal gene into the bone marrow of people with sickle cell anemia will result in normal hemoglobin. Scientists are also exploring the possibility of turning off the defective gene while reactivating another gene responsible for the production of fetal hemoglobin —a type of hemoglobin found in newborns that prevents sickle cells from forming.Potential treatments using gene therapy are a long way off, however.
   
• Nitric oxide: People with sickle cell anemia have low levels of nitric oxide in their blood. Nitric oxide is a gas that helps keep blood vessels open and reduces the stickiness of red blood cells. Treatment with inhaled nitric oxide might prevent sickle cells from clumping together. Studies on nitric oxide have shown little benefit so far.
   
• Medication to boost fetal hemoglobin production: Researchers are studying various drugs to devise a way to boost the production of fetal hemoglobin. This is a type of hemoglobin that stops sickle cells from forming.

Taking the following steps to stay healthy may help you avoid complications of sickle cell anemia:

• Take folic acid supplements daily, and choose a healthy diet. Bone marrow needs folic acid and other vitamins to make new red blood cells. Your doctor might recommend a folic acid supplement. Choose a diet that focuses on a variety of colorful fruits and vegetables, as well as whole grains.
• Drink plenty of water. Dehydration can increase your risk of a sickle cell crisis. Drink water throughout your day, aiming for about eight glasses a day. Increase the amount of water you drink if you exercise or spend time in a hot, dry climate.
• Avoid temperature extremes: Exposure to extreme heat or cold can increase your risk of a sickle cell crisis.
• Exercise regularly, but don't overdo it. Talk with your doctor about how much exercise is right for you.
• Use over-the-counter (OTC) medications with caution. Use OTC pain medications, such as ibuprofen (Advil, Motrin IB, Children's Motrin, others) or naproxen sodium (Aleve) sparingly, if at all, because of the possible effect on your kidneys. Ask your doctor before taking OTC drugs.

SCD has a high prevalence in India, especially in the central and western regions, and poses a considerable health burden. With increasing control of infant mortality and infectious diseases, genetic diseases are assuming a proportionately greater importance; the beta thalassaemias, sickle cell disease, and haemoglobin E disease contribute significantly to morbidity and mortality in India. The natural history of SCD is not established. About 20 per cent of children with sickle disease died by the age of two as reported in one ICMR survey, and 30 per cent children with SCD among the tribal community die before they reach adulthood.

1. Mayo Clinic - Sickle Cell Anemia 
2. how is sickle cell anemia inherited?