What is Sickle Cell Disease?

Sickle cell disease (SCD) is the most common inherited blood disorder. That means it’s passed down through families. You’re born with SCD. It is not something you catch or develop later in life.

The disease gets its name because when you have SCD, your red blood cells look like a sickle, which is a C-shaped farm tool.

Red blood cells contain a molecule called hemoglobin, which carries oxygen throughout the body. In a healthy person, hemoglobin is smooth, round, and flexible. That allows red blood cells to glide easily through your bloodstream. But if you have SCD, the hemoglobin’s shape is abnormal. It forms rods that clump together. That causes red blood cells to become rigid and curved. The odd-shaped cells block blood flow. It’s dangerous, and can cause extreme pain, anemia, and other symptoms.

About 100,000 people in the United States have sickle cell disease. Most of them are African-Americans.

What Causes Sickle Cell Disease?

A problem in the hemoglobin-beta gene found on chromosome 11. The defect forms abnormal hemoglobin molecules.

Both your parents need to pass the abnormal hemoglobin gene on to you in order for you to develop the disease. If both your parents carry the defective gene, you have a 1 in 4 chance of inheriting the disease and becoming sick with it.

If a child is born with one defective hemoglobin-beta gene, he may become a carrier of the disease. Carriers usually don’t develop SCD symptoms. But, they can pass the disease on to future children if their partner also carries the sickle cell trait.

Types of Sickle Cell Disease

There are several different forms of sickle cell disease. The type you or your child inherit depends on many things, including the specific type of abnormal hemoglobin you have.

Hemoglobin SS, also called sickle cell anemia, is usually the most severe type of this disorder.

Other common forms include:

  • Hemoglobin SC (usually mild)
  • Hemoglobin Sβ thalassemia

Rare types are:

  • Hemoglobin SD
  • Hemoglobin SE
  • Hemoglobin SO

In the U.S., newborn screening programs require that all babies are tested for sickle cell disease shortly after birth.

WebMD Medical Reference Reviewed by Minesh Khatri, MD on May 07, 2019



National Human Genome Research Institute: “Learning About Sickle Cell Disease.”

National Heart, Lung, and Blood Institute: “Sickle Cell Anemia,” “How is Sickle Cell Disease Diagnosed?”

Mayo Clinic: “Sickle Cell Anemia.”

CDC: “Facts About Sickle Cell Disease.”

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