Sickle Cell Disease & Trait

Sickle cell disease is a genetically inherited, potentially life-threatening blood disorder that affects a special molecule inside the red blood cells called hemoglobin. Hemoglobin carries oxygen in red cells and helps to transport oxygen from the lungs to the organs of the human body. When the sickle type of hemoglobin is exposed to stressful situations, even as simple as cold weather, the red cells change shape and are unable to carry normal amounts of oxygen to the body. Instead of being smooth and round, the cells become hard, sticky, and break easily. When these misshaped cells enter the capillary system, they are not flexible to get through, clump together, and subsequently block blood vessels, thus reducing the amount of oxygen available to the body. This causes severe pain, blood vessel, and organ damage. Sickle red blood cells have an average lifespan of 8-40 days as opposed to normal cells, which have a lifespan of 120 days.  Pain crisis can occur in any part of the body. Persons with the disease are extremely vulnerable to infections. They may also suffer from jaundice, deterioration of joints, kidney failure, infections, recurrent severe pain episodes, strokes, blindness, life-threatening enlargement of the spleen, and a shortened life expectancy. The median age of life for women with sickle cell disease is just 45 years, while it is even less at 40 years for men.

 

What is Sickle Cell Trait?

Someone who inherits the hemoglobin S gene from one parent and normal hemoglobin (A) from the other parent will have sickle cell trait. People with sickle cell trait do not usually have the symptoms of true sickle cell anemia. They are simply carriers of sickle cell disease. Patients with a combination of HbS and thalassemia trait, or with any abnormal hemoglobin (C, D, E, O), may experience a disease that is similar to sickle cell disease. Genetic counseling is recommended for all carriers of sickle cell trait, thalassemia trait, and/or any abnormal hemoglobin. It is possible to diagnose sickle cell anemia in early part of pregnancy.

 

Countries affected by Sickle Cell Disease

About 1 in 12 African Americans has sickle cell trait. It is also common in Africa, Portugual, Spain, French Corsica, Sardinia, Sicily, Italy, Greece, Turkey, Lebanon, Israel, Saudi Arabia, Kuwait, Yemen, India and Sri Lanka.

 

Types of Sickle Cell Disease

There are different forms of hemoglobin that can cause someone to have symptoms similar to sickle cell disease, but hemoglobin SS, SC disease and sickle beta thalassemia are the most common.

Hemoglobin SS is homozygous sickle cell disease. The hemoglobin S is inherited from both parents. It has moderate to severe symptoms, and more severe anemia than other forms of Sickle Cell Disease. The life expectancy is in the mid 40′s.

Hemoglobin SC is heterozygous for sickle cell disease.  Hemoglobin S is inherited from one parent and hemoglobin C is inherited from the other parent. Hb SC has less severe anemia than Hb SS. The life expectancy is in the mid 60′s.

Sickle beta thalassemia is heterozygous for sickle cell disease.  Hemoglobin S is inherited from one parent and the beta thalassemia gene from the other. There are 2 types of sickle beta thalassemia.

 

  • The sickle beta plus thalassemia has little production of the beta-globin required for the formation of red blood cells. This decreases the hemoglobin production and the size of the red blood cells. It is a less severe condition than sickle beta zero thalassemia.
  • The sickle beta zero thalassemia is due to lack of beta gene required for the formation of normal hemoglobin in red blood cells.  It is more severe and commonly resembles the symptoms of sickle cell anemia (SS). However, in some cases the symptoms of beta-zero thalassemia are worse than those seen in homozygous sickle cell disease and is often associated with a poor prognosis.

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