What Is Sickle Cell Disease?

Sickle cell disease is an inherited disorder that affects red blood cells. People with the disease produce a faulty version of hemoglobin — the protein that carries oxygen throughout the body. Defective hemoglobin — known as hemoglobin S — causes normally oval-shaped red blood cells to assume a sickle-like shape, from which the disease gets its name.

One key problem with these sickle-shaped cells is that they don’t move properly through the blood vessels. The resulting blockages can obstruct blood flow and lead to other disease symptoms.

Causes of sickle cell disease

Sickle cell disease is caused by mutations in the beta-globin (HBB) gene that contains instructions to make a component of hemoglobin. In people with sickle cell disease, at least one HBB gene copy contains instructions for making hemoglobin S, while the second gene copy may contain instructions for making another faulty version of the protein, such as hemoglobin C.

The disorder is inherited in an autosomal recessive manner, meaning that a person must inherit two abnormal copies of the HBB gene — one from each parent — to develop the condition. People with a faulty gene from only one parent do not develop sickle cell disease, but instead have what is known as the sickle cell trait. These individuals usually do not show any symptoms of sickle cell, but can still pass the condition on to their biological children.

Symptoms of sickle cell disease

Red blood cells containing faulty hemoglobin can become misshapen and rigid, making it difficult for them to pass through small blood vessels, slowing or blocking blood flow. This in turn can compromise oxygen delivery to different tissues and organs, causing damage and inflammation. Blood vessel blockage also can result in episodes of sudden and severe pain, known as vaso-occlusive crises (VOCs).

Sickled red blood cells usually break apart and die much quicker than healthy rounded red blood cells. Because these cells are destroyed faster than they are made, people with sickle disease often have a shortage of red blood cells — a condition known as anemia, the most common symptom of the sickle cell.

People with sickle cell also may experience swelling in the hands and feet, and vision problems. In addition, their growth can be delayed, and they often are more prone to infections.

Diagnosis of sickle cell disease

Sickle cell disease is diagnosed with a blood test that looks for abnormal hemoglobin proteins. In many countries, including the U.S., this type of test is part of routine newborn screening programs.

The condition also can be diagnosed in an unborn baby by testing a small sample of amniotic fluid — the liquid that surrounds the baby in the womb — or the mother’s placenta. These prenatal tests look for the presence of the mutated HBB gene instead of defective hemoglobin proteins.

Treating sickle cell disease

A stem cell transplant, a procedure that involves replacing a patient’s blood cell precursors with those taken from a healthy donor, is the only treatment currently available to cure sickle cell disease. Such transplants are complex, however, and like all treatments, carry risks and requirements.

There are several other treatments that can relieve pain and prevent complications.

Commonly used medications include antibiotics to prevent infections and painkillers to manage pain. Some treatments also are available to reduce the frequency of pain crises, including hydroxyurea and Adakveo (crizanlizumab). Several gene therapies also are being developed and evaluated as potential treatments for sickle cell.


Last updated: Sept. 16, 2021


Sickle Cell Disease News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.