sickle cell anemia

sickle cells

The sickle-shaped red blood cells tend to get stuck in blood vessels, blocking the flow of blood.

inheriting sickle cell genes

The presence of two sickle cell genes (SS) is needed for sickle cell anemia. If each parent carries one sickle hemoglobin gene (S) and one normal hemoglobin gene (A), with each pregnancy, there is a 25% chance of the child's inheriting two SS genes and having sickle cell anemia; a 25% chance of inheriting two AA genes and not having the disease or being a carrier; and a 50% chance of being an unaffected carrier (AS) like the parents.

normal and sickled blood flow

Figure A shows normal red blood cells flowing freely in a blood vessel. The inset image shows a cross-section of a normal red blood cell with normal hemoglobin. Figure B shows abnormal, sickled red blood cells clumping and blocking blood flow in a blood vessel. (Other cells also may play a role in this clumping process.) The inset image shows a cross-section of a sickle cell with abnormal hemoglobin.

Sickle cell anemia is a serious disease in which the body makes abnormally shaped red blood cells. Normal red blood cells are smooth and round like a doughnut without a hole. They move easily through blood vessels to carry oxygen to all parts of the body. In sickle cell anemia, the body produces red blood cells that are shaped like a sickle (or crescent). These "sickle cells" are hard and sticky and they don't move easily through blood vessels. They tend to get stuck and block the flow of blood to the limbs and organs. This can cause pain, organ damage, and a low blood count (anemia).


Sickle cell anemia is an inherited (genetic) disorder seen most commonly in people of African ancestry. The disorder is caused by a single base pair change in one of the genes that codes for hemoglobin, the blood protein that carries oxygen. People who have sickle cell anemia are born with it. It is a lifelong disease.


Sickle cell anemia affects millions of people. Effective treatments exist for the symptoms and complications of the disease, but in most cases there is no cure. (Some researchers believe that bone marrow transplantation may offer a cure in a small percentage of cases.) Over the past 30 years, doctors have learned a great deal about the disease. They know what causes it, how it affects the body, and how to treat many of the complications. Today, with good health care, many people with the disease:


  • Are in reasonably good health much of the time
  • Live fairly normal lives
  • Live 40 to 50 years or more


    Anemia is the term for having a shortage of red blood cells in the blood. In sickle cell anemia, this shortage of red blood cells occurs because sickle cells do not last very long. Red blood cells are produced in the spongy marrow inside the large bones of the body. The bone marrow constantly makes new red blood cells to replace old ones. Normal red blood cells last about 120 days in the bloodstream and then die. Sickle cells die much faster, usually after only about 10 to 20 days. The bone marrow can't make new red blood cells fast enough to replace the dying ones, so anemia (low level of red blood cells) results.


    Sickle cell trait versus anemia

    The condition called sickle cell trait is different from sickle cell anemia. A person with sickle cell trait does not have the disease but carries the gene that causes the disease. People with sickle cell trait can pass the gene on when they have children.


    Children who inherit only one copy of the sickle cell gene (from one parent) will not have sickle cell anemia. They will have sickle cell trait.


    People with sickle cell trait:


  • Generally have no symptoms
  • Live normal lives
  • Can pass the sickle cell gene on to their children

    When two people with sickle cell trait have a baby, there is a:


  • One in four chance (25%) the baby will inherit two sickle cell genes and have the disease.
  • One in four chance (25%) the baby will inherit two normal genes and not have the disease or trait.
  • Two in four chance (50%) the baby will inherit one normal gene and one sickle cell gene. The baby will not have the disease but will have sickle cell trait like the parents.

    Who is at risk?

    Sickle cell anemia affects millions of people throughout the world. It is common in people whose families come from any of these areas of the world:


  • Parts of Africa (the region south of the Sahara Desert)
  • Spanish-speaking areas, such as South America, Cuba, and Central America
  • Saudi Arabia
  • India
  • Mediterranean countries, such as Turkey, Greece, and Italy

    In the United States, sickle cell anemia affects about 72,000 people. The families of most Americans who are affected come from Africa. In the United States, the disease occurs in about:


  • One in every 600 African-American births
  • One in every 1,000–1,400 Hispanic-American births
  • About 2 million Americans have sickle cell trait. About 1 in 12 African Americans has sickle cell trait.

    Signs and symptoms

    The signs and symptoms of sickle cell anemia are different in each person. Some people have mild symptoms. Others have very severe symptoms and are often hospitalized for treatment.


    The most common signs or symptoms are related to:


  • Anemia
  • Pain when sickle-shaped red blood cells block the flow of blood to an organ
  • Other more specific symptoms

    The general signs or symptoms of anemia are:


  • Fatigue (feeling very tired)
  • Paleness
  • Jaundice (yellowing of the skin and eyes)
  • Shortness of breath

    Pain is the symptom of sickle cell anemia that most people know. In both children and adults, pain may result from blocked flow of blood and oxygen. Painful events may occur in any body organ or joint. Some patients have these painful crises less than once a year. Others may have 15 or more crises in a year. The pain can be acute (sudden), chronic (long lasting), or a mixture of the two.


  • Acute pain is the most common type of pain. This is sudden pain that can range from a mild ache to very severe pain. The pain usually lasts from hours to a few days. With complications or poor treatment, the pain can last for weeks.

  • Chronic pain usually lasts 3 to 6 months or longer. Chronic pain can be hard to bear and mentally draining. This pain may severely limit daily activities.

  • Mixed pain is a combination of both acute and chronic pain.

    Other complications of sickle cell anemia include:


  • Hand-foot syndrome. When the small blood vessels in hands or feet are blocked by sickle cells, pain and swelling can occur, along with fever. One or both hands and/or feet may be affected at the same time. This may be the first symptom of sickle cell anemia in infants. Pain may be felt in the many bones of the hands and feet. Swelling usually occurs on the back of the hands and feet and moves into the fingers and toes.

  • Eye problems. The retina, a thin layer of tissue at the back of the eye, receives and processes visual images. When the retina does not get enough blood, it can weaken and cause problems. These problems can be serious enough to cause blindness.

  • Infections. Both children and adults with sickle cell anemia have a hard time fighting infections. The spleen is an organ in your body that helps fight infection. In sickle cell anemia, the spleen can become damaged and unable to do its job. Infants and young children with a damaged spleen are more likely to get infections that can kill them within hours or days. Pneumonia is the most common cause of death in young children with sickle cell anemia. Meningitis, influenza, and hepatitis are other infections that are common in people with sickle cell anemia.

  • Acute chest syndrome. This is a life-threatening problem of sickle cell anemia. This syndrome is similar to pneumonia. It is caused by infection or by sickle cells trapped in the lungs. Patients usually have chest pain, fever, and an abnormal chest X-ray.

  • Delayed growth and puberty in children. Children with sickle cell anemia often grow more slowly and reach puberty later than other children. The slow rate of growth is caused by a shortage of red blood cells (anemia). Adults with sickle cell anemia often are slender or small in size. Sores (ulcers) on the legs. Sickle cell ulcers usually begin as small, raised, crusting sores on the lower third of the leg. Leg sores occur more often in males than in females and usually appear between ages 10 and 50. The cause of leg ulcers is unclear. There can be just one ulcer or many. Some heal rapidly, but others persist for years or come back after healing.

  • Stroke. The sickle-shaped red blood cells may stick to the walls of the tiny blood vessels in the brain. This can cause a stroke. This type of stroke occurs mainly in children. The stroke can cause learning disabilities or more severe problems.

  • Gallstones. Gallstones form in the gall bladder when there is too much bilirubin in the body. Bilirubin is made when red blood cells break down. People with gallstones may have steady pain that lasts for 30 minutes or more in the upper right side of the belly, under the right shoulder, or between the shoulder blades. The pain may occur after eating fatty meals. The patient may have nausea, vomiting, fever, sweating, chills, clay-colored stool, and yellowish color of the skin or whites of the eyes.

  • Priapism. Males with sickle cell anemia may have painful and unwanted erections called priapism. This happens because the sickle cells stop blood flow out of an erect penis.


    Forty-four States, the District of Columbia, Puerto Rico, and the Virgin Islands currently test all newborns for sickle cell anemia. This testing is available by request in the other six States. The test can show if the newborn infant has sickle cell anemia or carries the sickle cell trait. The test uses blood from the same blood samples as other routine newborn screening tests. If the first test shows that the sickle-shaped hemoglobin is present, a second blood test is done to confirm the diagnosis.


    Early diagnosis of sickle cell anemia is very important so that children who have the disease can get proper treatment.


    It is also possible to identify sickle cell anemia before birth. This is done by getting a sample of amniotic fluid or tissue taken from the placenta. This test can be done as early as the first few months of pregnancy.



    Effective treatments exist for the symptoms and complications of sickle cell anemia, but in most cases there is no cure. Some researchers believe that bone marrow transplantation may offer a cure in a small percentage of cases. Researchers are working on developing new treatments for sickle cell anemia, including gene therapy and more safe and effective bone marrow transplants.


    People with sickle cell anemia need regular medical care. Some doctors and clinics specialize in treating people with the disease.


    The goals of treating sickle cell anemia are to relieve pain, prevent infections, and control complications if they occur. The treatments include:


  • Medicines
  • Blood transfusions
  • Specific treatment for complications

    Treating pain

    Painful crises are the leading cause of emergency room visits and hospitalizations of people with sickle cell anemia. The usual treatments for acute pain crises are pain-killing medicines and fluids, either by mouth or through a vein, to prevent dehydration. The pain-killing medicines most often used are:


  • acetaminophen
  • non-steroidal anti-inflammatory drugs (NSAIDs)
  • opioids, such as morphine, oxycodone, hydrocodone, and others

    The treatment of patients with mild-to-moderate pain usually begins with NSAIDs or acetaminophen. If pain continues, an opioid may be added. Moderate-to-severe pain is treated with opioids. The opioid may be used alone or together with NSAIDs or acetaminophen.


    In adult patients with severe sickle cell anemia, doctors may give a medicine called hydroxyurea to reduce the frequency of painful crises. This medicine is used only to prevent these crises, not to treat them when they occur. Given daily, it can reduce the frequency of painful crises and of acute chest syndrome. Patients taking the medicine may also need fewer blood transfusions. Patients taking hydroxyurea must be monitored carefully because the medicine can cause serious side effects, including an increased risk of dangerous infections. Because of the risks of the medicine, it is usually only used in adults with severe complications of sickle cell anemia. It is not approved for use in children.


    Preventing infections

    Infection is a major complication of sickle cell anemia. In fact, pneumonia is the leading cause of death in children with the disease. Other infections common in people with the disease include meningitis, influenza, and hepatitis.


    To prevent infections in babies and young children, treatments include:


  • Daily doses of penicillin. Treatment may begin as early as 2 months of age and continue until the child is at least 5 years old.
  • Vaccinations for pneumonia, meningitis, influenza, and hepatitis.

    Children with sickle cell anemia should have a flu shot each year. If a child with sickle cell anemia shows early signs of an infection, such as fever, it is very important to get treatment right away.


    Adults with sickle cell anemia should also have a flu shot every year. In addition, they should be vaccinated for pneumonia.


    Preventing eye damage

    Children may develop damage to the blood vessels in the back of their eyes. Parents should ask the child's doctor about regular checkups with an eye doctor who specializes in diseases of the retina. The retina is a thin layer of tissue inside the back of the eye.


    Blood transfusions

    Blood transfusions are used to treat worsening anemia and sickle cell complications. A sudden worsening of anemia resulting from infection or enlargement of the spleen is a common reason for a transfusion. Some, but not all, patients need transfusions to prevent life-threatening events such as stroke or pneumonia.


    Treating complications

    Acute chest syndrome is a frequent cause of death in children and adults with sickle cell anemia. Treatment usually requires hospitalization and may include oxygen therapy, transfusions, antibiotics, and pain medicine.


    Hand-foot syndrome is an early complication seen in sickle cell anemia. The syndrome may start at less than 1 year of age. Treatment includes the use of pain medicine and fluids.


    Leg ulcers may be treated with cleansing solutions and medicated creams or ointments. Skin grafts may be needed if the condition continues. Leg ulcers can be painful, and patients may be given strong pain medicine. Bed rest and keeping the leg raised to reduce swelling are useful, although not always possible.


    Regular health care for children

    Children with sickle cell anemia should get regular health care, just like children without the disease. They need to have their growth checked and to get the usual shots that all children receive.


    Before age 2, children with sickle cell anemia should see the doctor every 2 or 3 months. After age 2, children should see the doctor at least every 6 months. These visits are good chances for parents to talk with their child's health care provider and ask questions about the child's care.


    Penicillin is generally given to all children with sickle cell anemia until age 5. Many patients are prescribed a vitamin called folic acid (folate) to help prevent some of the complications of sickle cell anemia.


    New treatments

    Today, research on sickle cell anemia is looking at new medicines, bone marrow transplants, and gene therapy. The hope is that these studies can provide new treatments and find a possible cure for sickle cell anemia. Researchers are also looking for a way to predict the severity of the disease.


    Bone marrow transplant can be a very effective treatment for sickle cell anemia, but, because of its risks, only some patients can or should have this procedure. The bone marrow transplant procedure carries the risk of serious complications and even death. It is usually reserved for younger patients with severe disease, but the decisions are made on a case-by-case basis. It requires a donation of bone marrow from a closely matched donor, usually a close family member, who does not have the disease.


    Living with sickle cell anemia

    If you have sickle cell anemia, it is important to take good care of yourself and see your doctor regularly. Things you need to do to take care of your health include:


  • Maintain a healthy diet. Your doctor may also give you a vitamin (folic acid) to take every day to help your body make new red blood cells.
  • Drink adequate water every day.
  • Get enough sleep and rest.
  • See your doctor regularly for checkups and treatment.
  • Get a flu shot and other vaccinations to prevent infections.
  • See your dentist regularly to prevent loss of teeth and infections.
  • Educate yourself about your disease and learn what signs of problems to watch out for.
  • Avoid overexertion, stress, and extremes of heat or cold.

    Caring for a child with sickle cell anemia

    If your child has sickle cell anemia, you should learn as much about the disease as possible. This will help you recognize early signs of problems, such as fever or chest pain, and seek early treatment. Sickle cell centers and clinics can provide information and counseling to help you handle the stresses of coping with this serious chronic disease.


    Make sure that your child gets daily penicillin up to age 5 to prevent serious infections. Children should also have a flu shot every year and a vaccination against pneumonia. Keep a thermometer on hand, and know how to use it. Call a doctor if your child has a temperature above 101°F (38.5°C). Talk to your child's doctor about your child's treatment and the best ways to help keep your child as healthy as possible.


    School-aged children should participate in physical education. Teachers should allow children with sickle cell anemia to rest if they tire and to drink fluids after exercise. Children and teenagers may also play competitive sports. Coaches should watch for signs of fatigue and allow the athlete to rest.


    Education and job training

    If you have sickle cell anemia, it is important that you complete your education. You should not seek jobs that require strenuous work, long work hours, or exposure to extreme temperatures.


    Genetic counseling

    People who are planning to have children should find out if they have sickle cell trait (which means they carry the sickle cell gene). If both parents have sickle cell trait, they should get genetic counseling. The counselor can tell what the chances are that their child will have sickle cell trait or sickle cell anemia. Accurate diagnostic tests and information are available from health departments, neighborhood health centers, medical centers, and clinics that care for people with sickle cell anemia.


    With good health care, many people with sickle cell anemia are in reasonably good health much of the time and can live productive lives. People with sickle cell anemia are living longer today than in the past. Many patients with sickle cell anemia now live into their forties, fifties, and beyond.