Get The Facts About Sickle Cell

Q1. What is sickle cell trait and who is affected by it?

A1. Sickle cell trait happens when a person inherits a copy of the sickle hemoglobin gene from one parent and a normal hemoglobin gene from the other parent. People with sickle cell trait are carriers of the sickle hemoglobin gene and they can pass it on when they have a child. A person who inherits two copies of the sickle hemoglobin gene—one from each parent—has sickle cell disease (SCD).

About 1 in 13 Blacks in the United States are born with sickle cell trait.

Please see the below example of an inheritance pattern.

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Q2. How will a person know if he or she has sickle cell trait? How is it diagnosed?

A2. Sickle cell trait is diagnosed by genetic testing performed during pregnancy, as a newborn, or later in life. This testing looks for the sickle hemoglobin gene rather than the abnormal hemoglobin protein.

Some prenatal testing before birth can be done as early as 8–10 weeks into the pregnancy. Other prenatal testing, done later in pregnancy, takes a sample of amniotic fluid, the liquid in the sac surrounding a growing baby, or tissue taken from the placenta, the organ that attaches the umbilical cord to the mother’s womb.

Every state in the United States, the District of Columbia, and the U.S. territories require that every baby have a blood test as part of a newborn screening program for SCD. Because this screening looks for the sickle hemoglobin gene, it can also determine if a child has sickle cell trait. Newborn screening results are sent to the doctor who ordered the test and to the child’s primary doctor.

Anyone who does not know if they have sickle cell trait can have a genetic test to find out if they have the sickle hemoglobin gene.

For more information, visit NHLB’s website:

Q3. What is sickle cell disease and is it different from sickle cell trait? Who is affected by it?

A3. Sickle cell disease describes a group of inherited red blood cell disorders. People with sickle cell disease have abnormal hemoglobin, called hemoglobin S or sickle hemoglobin, in their red blood cells. Hemoglobin is a protein in red blood cells that carries oxygen throughout the body.

Yes, there is a difference between sickle cell trait and SCD. People with sickle cell trait inherit one copy of the sickle hemoglobin, and people with SCD inherit two copies of the sickle hemoglobin gene (one from each parent) or one copy of sickle hemoglobin with another abnormal hemoglobin (C, beta-thalassemia, or E). Sickle cell trait is not a mild form of sickle cell disease.

There are six different types of sickle cell disease. For example, sickle cell anemia or hemoglobin SS is the most common form of SCD. Other types of SCD, such as hemoglobin SC and hemoglobin sickle beta thalassemia and can occur in people of Hispanic, southern European, Middle Eastern, or Asian Indian backgrounds.

SCD affects millions of adults and children around the world. SCD affects an estimated 90,000 to 100,000 people in the United States, mainly African Americans, and occurs in about 1 out of every 365 African American births.
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Q4. Can sickle cell trait ever evolve or convert to sickle cell disease?

A4. No, sickle cell trait cannot evolve or convert to SCD. A person with sickle cell trait inherits a sickle hemoglobin from only one parent. In order for a person to have sickle cell disease, they must inherit two sickle hemoglobins, one from each parent.

Q5. What is sickle cell anemia?

A5. Sickle cell anemia is the most common form of SCD. People who have sickle cell anemia inherit two abnormal hemoglobin S genes.

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Q6. What are the signs and symptoms of sickle cell anemia? What are the health complications?

A6. Sickle cell anemia signs and symptoms are the same as SCD signs and symptoms. If a person has SCD, it is present at birth. Because all newborn babies in the United States, the District of Columbia, and the U.S. territories have newborn screening, parents are notified before the child has symptoms. Most infants do not have any problems from the disease until they are about 5 or 6 months of age.

The signs and symptoms of SCD will vary from person to person and can change over time. Most of the signs and symptoms of SCD are related to complications of the disease.

Some children with SCD will start to have problems early on and some later. Early symptoms of SCD may include:
• Painful swelling of the hands and feet
• Fatigue or fussiness from anemia
• A yellowish color of the skin or whites of the eyes

Major complications of SCD may include:

• Acute Pain – Pain episodes can occur without warning when sickled red blood cells block blood flow and decrease oxygen delivery.

• Chronic Pain – This type of pain is ongoing and is usually different from crisis pain or the pain that results from organ damage. Chronic pain can be severe and can make life difficult. Researchers and doctors are still trying to understand more about chronic pain and sickle cell disease.

• Severe Anemia – People with SCD usually have mild to moderate anemia. At times, however, they can have severe anemia. Severe anemia can be life threatening.

• Infections – The spleen is important for protection against certain kinds of germs. Sickle cells can damage the spleen and weaken or destroy its function early in life. People with SCD who have damaged spleens are at risk for serious bacterial infections.

• Acute Chest Syndrome – Sickling in blood vessels of the lungs can deprive a person’s lungs of oxygen. When this happens, areas of lung tissue are damaged and cannot exchange oxygen properly. This condition is known as acute chest syndrome. In acute chest syndrome, at least one segment of the lung is damaged. Acute chest syndrome can also occur as a complication of an acute pain episode.

• Stroke – People with SCD can have a stroke even as children. This happens when brain cells are damaged when blood flow is blocked to the brain. Sometimes, a stroke happens and the person does not have any signs or symptoms. A stroke can lead to problems with learning and decision making.

• Eye Problems – SCD can injure blood vessels in the eye leading to problems with vision.

• Heart Disease – People with SCD can have problems with blood vessels in the heart and with heart function. The heart can become enlarged. People can also develop pulmonary hypertension, a type of high blood pressure that affects blood vessels in the lungs and in the heart.

• Kidney Problems – SCD causes the kidneys to have trouble making the urine as concentrated as it should be. This may lead to a need to urinate often and to have bedwetting or uncontrolled urination during the night.

• Priapism – Men with SCD can have unwanted, sometimes prolonged, painful erections. This condition is called priapism. If it goes on for a long period of time, priapism can cause permanent damage to the penis.

• Liver Complications – There are a number of ways in which the liver may be injured in SCD. For example, Sickle cell intrahepatic cholestasis is an uncommon, but severe, form of liver damage that occurs when sickled red cells block blood vessels in the liver.

• Leg Ulcers – Ulcers are sores that usually start small and then get larger and larger. People with SCD usually don’t get ulcers until after the age of 10.

• Joint Complications – Sickling in the bones of the hip and, less commonly, the shoulder joints, knees, and ankles, can decrease oxygen flow and result in severe damage in these bones. Symptoms include pain and problems with walking and joint movement.

• Delayed Growth and Puberty – Children with SCD may grow and develop more slowly than their peers because of anemia. They will reach full sexual maturity, but this may be delayed.

• Mental Health – As in other chronic diseases, people with SCD may feel sad and frustrated at times. The limitations that SCD can impose on a person’s daily activities may cause them to feel isolated from others. Sometimes they become depressed.

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Q7. Can a woman with sickle cell disease have a safe pregnancy? Would the baby be at risk of having the disease?

A7. Pregnancies in women with SCD can be risky for both the mother and the baby. Pregnant women who have SCD should always see an obstetrician, (OB), who has experience with SCD and high-risk pregnancies and deliveries. The OB should work with a hematologist or primary medical doctor who is well informed about SCD and its complications.

A pregnant woman with SCD will pass the sickle cell gene on to her child. If both parents have SCD, the child will inherit SCD.

Couples who are planning to have children, who know they have a risk of having a child with sickle cell disease (SCD), may want to meet with a genetics counselor. A genetics counselor can answer questions about the risk and explain the choices that are available.

Remember that when a child has sickle cell trait or SCD, a future sibling, or the child’s own future child, may be at risk. These possibilities should be discussed with the primary care doctor, a blood specialist called a hematologist, and/or a genetics counselor.

Please see the below example of an inheritance pattern.

For more information, visit NHLB’s website:

Q8. How is sickle cell disease treated?

A8. Currently, there are two disease modifying treatment options, hydroxyurea and blood transfusions, and one potential cure, stem cell transplants, which is still being refined and not yet widely available. To learn more about these treatment options, visit the NHLBI website:

Babies with SCD should be referred to a doctor or provider group that has experience taking care of people with this disease. The doctor might be a hematologist (a doctor with special training in blood diseases) or an experienced general pediatrician, internist, or family practitioner.

For infants, the first SCD visit should take place before 8 weeks of age.

If someone was born in a country that doesn’t perform newborn SCD screening, he or she might be diagnosed with SCD later in childhood. These people should also be referred as soon as possible for special SCD care.

All people who have SCD should see their SCD care providers regularly. Regularly means every 3 to 12 months, depending on the person’s age and disease severity. The SCD doctor or team can help to prevent problems by:

• Examining the person
• Giving medicines and immunizations
• Performing tests
• Educating families about the disease and what to watch out for

Q9. Is there a cure for sickle cell disease?

A9. At the present time, hematopoietic stem cell transplantation (HSCT) is the only cure for SCD. However, everyone with SCD may not be able to have a HSCT. Because only about 1 in 10 children with SCD has a matched donor without SCD in their families, the number of people with SCD who get transplants is low. HSCT is more risky in adults, and that is why most transplants are done in children.

There are several medical centers that are researching new SCD HSCT techniques in children and adults who don’t have a matched donor in the family or are older than most recipients. Hopefully, more people with SCD will be able to receive a transplant in the future, using these new methods.

Q10. Is there more information available on sickle cell?

A10. Yes, NHLBI has many useful sickle cell resources available. Visit the NHLBI website for more information about sickle cell disease.

In addition, NHLBI will be sponsoring a Sickle Cell Disease Forum from June 25 to 26, 2015. The purpose of this meeting is to bring together various organizations and individuals from the sickle cell disease community to discuss the issues impacting those living with the disease. We hope that the Forum will provide patients with a platform on which to share their opinions and experiences, which will not only help NHLBI to continue to refine its research planning efforts, but also allow them an opportunity to hear firsthand the community’s perspective on where research can make the greatest impact against the disease.

We encourage you to visit the Forum website to register to view the live webcast sessions.

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