Sickle Cell Anemia

Sickle cell anemia: Overview?
Sickle cell anemia, also called sickle cell disease, is a inherited blood disorder in which the body makes abnormal, sickle-shaped red blood cells. Patient with sickle cell disease have red blood cells that contain mostly hemoglobin S, an abnormal type of hemoglobin. Hemoglobin molecules tend to clump together, making red blood cells sticky, stiff, and more fragile, and causing them to form into a curved, sickle shape.

Normal red blood cells are disc-shaped and look like doughnuts without holes in the center. They move easily through your blood vessels. Red blood cells contain the protein hemoglobin. This iron-rich protein gives blood its red color and carries oxygen from the lungs to the rest of the body. In sickle cell anemia, which are usually smooth and donut-shaped, sickled red cells cannot squeeze through small blood vessels. Instead, they stack up and cause blockages that deprive organs and tissues of oxygen-carrying blood. This process produces periodic episodes of pain and ultimately can damage tissues and vital organs and lead to other serious medical problems. Normal red blood cells live about 120 days in the bloodstream, but sickled red cells die after about 10 to 20 days. Because the bone marrow can’t make new red blood cells fast enough to replace the dying ones.

People who inherit a sickle cell gene from one parent and a normal gene from the other parent have a condition called sickle cell trait. Sickle Cell trait (AS) is an inherited condition in which both hemoglobin A and S are produced in the red blood cells, always more A than S. Someone who inherits hemoglobin S from one parent and normal hemoglobin A from the other parent will have sickle cell trait. Someone who inherits hemoglobin S from one parent and another type of abnormal hemoglobin from the other parent will have another form of sickle cell disease, such as thalassemia.

What're causes of sickle cell anemia?
Sickle cell anemia is caused by hemoglobin S. Sickle cell anemia is inherited as an autosomal recessive trait. This means that both the mother and the father must pass on the defective form of the gene for a child to be affected. Most often, sickle cell disease is passed down the family tree by parents who have sickle cell trait.

People with sickle cell trait have one normal hemoglobin gene and one defective form of the gene. So their bodies make both normal hemoglobin and sickle cell hemoglobin. Their blood may contain some sickle cells, but they usually don't experience symptoms unless they're in an area with low oxygen, such as at high altitudes on an airplane or on a mountain. However, they are carriers of the disease, which means they can pass the defective gene on to their children.

If each parent carries one sickle hemoglobin gene (S) and one normal gene (A), each child has a 25% chance of inheriting two defective genes and having sickle cell anemia; a 25% chance of inheriting two normal genes and not having the disease; and a 50% chance of being an unaffected carrier like the parents.