Topic updated: June 2012

Sickle Cell Anemia

What Is Sickle Cell Anemia?

Sickle cell anemia (uh-NEE-me-uh) is the most common form of sickle cell disease (SCD). SCD is a serious disorder in which the body makes sickle-shaped red blood cells. “Sickle-shaped” means that the red blood cells are shaped like a crescent.

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 (HEE-muh-glow-bin). This iron-rich protein gives blood its red color and carries oxygen from the lungs to the rest of the body.

Sickle cells contain abnormal hemoglobin called sickle hemoglobin or hemoglobin S. Sickle hemoglobin causes the cells to develop a sickle, or crescent, shape.

Sickle cells are stiff and sticky. They tend to block blood flow in the blood vessels of the limbs and organs. Blocked blood flow can cause pain, serious infections, and organ damage.

Overview

Sickle cell anemia is one type of anemia. Anemia is a condition in which your blood has a lower than normal number of red blood cells. This condition also can occur if your red blood cells don’t contain enough hemoglobin.

Red blood cells are made in the spongy marrow inside the large bones of the body. Bone marrow is always making new red blood cells to replace old ones. Normal red blood cells last about 120 days in the bloodstream and then die. They carry oxygen and remove carbon dioxide (a waste product) from your body.

In sickle cell anemia, the number of red blood cells is low because sickle cells don't last very long. Sickle cells usually die after only about 10 to 20 days. The bone marrow can't make new red blood cells fast enough to replace the dying ones.

Sickle cell anemia is an inherited, lifelong disease. People who have the disease are born with it. They inherit two copies of the sickle cell gene - one from each parent.

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 is different from sickle cell anemia. People who have sickle cell trait don’t have the disease, but they have one of the genes that cause it. Like people who have sickle cell anemia, people who have sickle cell trait can pass the gene to their children.

Outlook

Sickle cell anemia has no widely available cure. However, treatments can help with the symptoms and complications of the disease. Blood and marrow stem cell transplants may offer a cure for a small number of people.

Over the past 100 years, doctors have learned a great deal about sickle cell anemia. They know its causes, how it affects the body, and how to treat many of its complications.

Sickle cell anemia varies from person to person. Some people who have the disease have chronic (long-term) pain or fatigue (tiredness). However, with proper care and treatment, many people who have the disease can have improved quality of life and reasonable health much of the time.

Due to improved treatments and care, people who have sickle cell anemia are now living into their forties or fifties, or longer.

Other Names for Sickle Cell Anemia

  • HbS disease
  • Hemoglobin S disease
  • Hemoglobin SS disease
  • Sickle cell disease (a broad term that includes sickle cell anemia)
  • Sickle cell disorders (a broad group of conditions that includes sickle cell anemia)
  • Sickling disorder due to hemoglobin S

What Causes Sickle Cell Anemia?

Sickle cell anemia is an inherited disease. People who have the disease inherit two genes for sickle hemoglobin—one from each parent.

Sickle hemoglobin causes red blood cells to develop a sickle, or crescent, shape. Sickle cells are stiff and sticky. They tend to block blood flow in the blood vessels of the limbs and organs. Blocked blood flow can cause pain, serious infections, and organ damage.

Sickle Cell Trait

People who inherit a sickle hemoglobin gene from one parent and a normal gene from the other parent have a condition called sickle cell trait. Their bodies make sickle hemoglobin and normal hemoglobin.

People who have sickle cell trait usually have few, if any, symptoms and lead normal lives. However, some people may have medical complications.

People who have sickle cell trait can pass the sickle hemoglobin gene to their children. The following image shows an example of an inheritance pattern for sickle cell trait.

Who Is At Risk for Sickle Cell Anemia?

Sickle cell anemia is most common in people whose families come from Africa, South or Central America (especially Panama), Caribbean islands, Mediterranean countries (such as Turkey, Greece, and Italy), India, and Saudi Arabia.

In the United States, it's estimated that sickle cell anemia affects 70,000–100,000 people, mainly African Americans. The disease occurs in about 1 out of every 500 African American births. Sickle cell anemia also affects Hispanic Americans. The disease occurs in more than 1 out of every 36,000 Hispanic American births.

More than 2 million Americans have sickle cell trait. The condition occurs in about 1 in 12 African Americans.

To read the rest of this article from the National Heart, Lung and Blood Institute

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