Sickle cell disease


Thanks to early diagnosis and advances in care, the outlook for people with sickle cell disease has improved greatly in the past 50 years.

In countries like the United States, with well-resourced health care systems, more than 90 percent of children with the disease live well into adulthood. The keys are learning how to take the best possible care of yourself and working closely with health care providers who understand your condition and challenges. 

Seattle Cancer Care Alliance (SCCA) offers comprehensive treatment for adults with sickle cell disease from a team of experts.

Children with sickle cell are treated at Odessa Brown Children’s Clinic, part of Seattle Children’s. Read about childhood sickle cell disease on Seattle Children’s website.

What is sickle cell disease?

Sickle cell disease is a group of inherited blood disorders that cause people to have an abnormal protein in their red blood cells (RBCs).

Normally, RBCs are flexible discs that can easily squeeze through small blood vessels. RBCs contain a protein called hemoglobin, which delivers oxygen to all cells throughout your body.

In sickle cell disease, your hemoglobin is different. It causes your RBCs to take on a crescent, or sickle, shape and become rigid. This leads to two main problems:

  • Sickle cells break apart easily. As a result, they die earlier than healthy RBCs (after about 10-20 days instead of the normal 90-120 days). Thus, your body may not have as many RBCs as you need. 
  • Sickle cells are sticky. They can clump together and adhere to the walls of your blood vessels, slowing or blocking the flow of blood — and delivery of oxygen — to some of your tissues and organs.

What causes sickle cell disease?

People with sickle cell disease are born with it because they inherited two abnormal hemoglobin genes, one from each parent.

If you inherit a sickle cell gene from only one parent and your other hemoglobin gene is normal, you have sickle cell trait. This means you carry the gene, and can pass it on to your own children, but you most likely do not have any signs of sickle cell disease yourself.

With genetic testing you can find out if you carry a gene that causes sickle cell.


Depending on the genes your parents passed on to you, you may have one of these types of sickle cell disease:

  • HbSS — Both your parents passed on an abnormal sickle hemoglobin gene (or hemoglobin S).
  • HbSC — One parent passed on an abnormal hemoglobin S gene, and the other parent passed on a gene for abnormal hemoglobin C.
  • HbS beta thalessemia — One parent passed on an abnormal hemoglobin S gene, and the other parent passed on a gene for beta thalessemia. There are two subtypes: HbS beta O-thalessemia and HbS beta +-thalessemia. (Beta is also written like this: β.)
  • HbSD — One parent passed on an abnormal hemoglobin S gene, and the other parent passed on a gene for abnormal hemoglobin D.
  • HbSE — One parent passed on an abnormal hemoglobin S gene, and the other parent passed on a gene for abnormal hemoglobin E.
  • HbSO — One parent passed on an abnormal hemoglobin S gene, and the other parent passed on a gene for abnormal hemoglobin O.


Sickle cell disease can lead to a number of symptoms and health problems. These can differ for each person and range from mild to severe. They tend to get worse over time.

Here are the main signs, symptoms and potential complications of sickle cell disease:

  • Painful episodes — Pain, caused by decreased oxygen to tissues (ischemia), is the most common problem. It tends to flare up in periods that doctors call “pain episodes” or “crises” and then subside. Episodes can come on suddenly, be mild to severe and last for any length of time. 
  • Anemia (low level of RBCs) — Anemia can make you tired, irritable, dizzy and lightheaded. It can lead to fast heart rate, breathing trouble and jaundice and make your skin paler than usual. In children, anemia can cause slow growth and delayed puberty.
  • Infection — Sickle cell disease increases your risk of infections, like flu, hepatitis, meningitis and pneumonia.
  • Hand-foot syndrome — This swelling of the hands and feet results from blocked blood vessels. You might also hear this called “dactylitis,” which refers to inflamed fingers or toes. You might have a fever as well.
  • Acute chest syndrome — This illness involves chest pain, coughing, breathing trouble and fever, similar to pneumonia. 
  • Organ damage — Sickle cells can lead to damage in many different organs, including your spleen, liver, heart, kidneys, lungs and eyes.
  • Stroke — Blood clots in veins (deep vein thrombosis, DVT) or the lungs (pulmonary embolism, PE) can block blood flow to your brain, causing a stroke.
  • Priapism — A painful erection that lasts for several hours can happen in sickle cell disease because of problems with blood flow.

Care for sickle cell is focused on preventing complications of the disease and managing any symptoms or health problems you do have. 


A simple blood test is all doctors need to diagnose sickle cell disease. In the U.S., most people are diagnosed right after birth through routine screening of newborns.

Sickle cell disease can also be diagnosed before birth. Families might choose to have testing if at least one of the baby’s parents knows they have sickle cell disease or sickle cell trait.

How common is sickle cell disease?

In the United States, about 100,000 people are living with sickle cell disease and about 3 million people have sickle cell trait. 

The disease is most common in African Americans. It affects 1 in every 365 African American babies born in the U.S. People from many other racial or ethnic groups are also at increased risk, including those whose ancestors came from sub-Saharan Africa, South America, the Caribbean, Central America, Saudi Arabia, India, Italy, Greece or Turkey.