Sickle cell anemia

DEFINITION

Sickle cell anemia is an inherited form of anemia — a condition in which there aren’t enough healthy red blood cells to carry adequate oxygen throughout your body.

Normally, your red blood cells are flexible and round, moving easily through your blood vessels. In sickle cell anemia, the red blood cells become rigid and sticky and are shaped like sickles or crescent moons. These irregularly shaped cells can get stuck in small blood vessels, which can slow or block blood flow and oxygen to parts of the body.

There’s no cure for most people with sickle cell anemia. However, treatments can relieve pain and help prevent further problems associated with sickle cell anemia.

CAUSES

Sickle cell anemia is caused by a mutation in the gene that tells your body to make hemoglobin — the red, iron-rich compound that gives blood its red color. Hemoglobin allows red blood cells to carry oxygen from your lungs to all parts of your body. In sickle cell anemia, the abnormal hemoglobin causes red blood cells to become rigid, sticky and misshapen.

The sickle cell gene is passed from generation to generation in a pattern of inheritance called autosomal recessive inheritance. This means that both the mother and the father must pass on the defective form of the gene for a child to be affected.

If only one parent passes the sickle cell gene to the child, that child will have the sickle cell trait. With one normal hemoglobin gene and one defective form of the gene, people with the sickle cell trait make both normal hemoglobin and sickle cell hemoglobin. Their blood may contain some sickle cells, but they generally don’t experience symptoms. However, they are carriers of the disease, which means they can pass the defective gene on to their children.

With each pregnancy, two people with sickle cell traits have:

• A 25 percent chance of having an unaffected child with normal hemoglobin
• A 50 percent chance of having a child who also is a carrier
• A 25 percent chance of having a child with sickle cell anemia

SYMPTOMS

Signs and symptoms of sickle cell anemia often don’t appear until an infant is at least 4 months old and may include:

• Anemia. Sickle cells are fragile. They break apart easily and die, leaving you without a good supply of red blood cells. Red blood cells usually live for about 120 days before they die and need to be replaced. But sickle cells die after an average of less than 20 days. This results in a lasting shortage of red blood cells (anemia). Without enough red blood cells in circulation, your body can’t get the oxygen it needs to feel energized. That’s why anemia causes fatigue.
• Episodes of pain. Periodic episodes of pain, called crises, are a major symptom of sickle cell anemia. Pain develops when sickle-shaped red blood cells block blood flow through tiny blood vessels to your chest, abdomen and joints. Pain can also occur in your bones. The pain may vary in intensity and can last for a few hours to a few weeks. Some people experience only a few episodes of pain. Others experience a dozen or more crises a year. If a crisis is severe enough, you may need to be hospitalized.
• Hand-foot syndrome. Swollen hands and feet may be the first signs of sickle cell anemia in babies. The swelling is caused by sickle-shaped red blood cells blocking blood flow out of their hands and feet.
• Frequent infections. Sickle cells can damage your spleen, an organ that fights infection. This may make you more vulnerable to infections. Doctors commonly give infants and children with sickle cell anemia vaccinations and antibiotics to prevent potentially life-threatening infections, such as pneumonia.
• Delayed growth. Red blood cells provide your body with the oxygen and nutrients you need for growth. A shortage of healthy red blood cells can slow growth in infants and children and delay puberty in teenagers.
• Vision problems. Some people with sickle cell anemia experience vision problems. Tiny blood vessels that supply your eyes may become plugged with sickle cells. This can damage the retina — the portion of the eye that processes visual images.

When to see a doctor

Although sickle cell anemia is usually diagnosed in infancy, if you or your child develops any of the following problems, see your doctor right away or seek emergency medical care:

• Unexplained episodes of severe pain, such as pain in the abdomen, chest, bones or joints.
• Swelling in the hands or feet.
• Abdominal swelling, especially if the area is tender to touch.
• Fever. People with sickle cell anemia have an increased risk of infection, and fever can be the first sign of an infection.
• Pale skin or nail beds.
• Yellow tint to the skin or whites of the eyes.
• Any signs or symptoms of stroke. If you notice any one-sided paralysis or weakness in the face, arms or legs, confusion, trouble walking or talking, sudden vision problems or unexplained numbness, or a headache, call 911 or your local emergency number right away.