ANEMIA, SICKLE CELL

Sickle cell anemia is a genetic disease in which the red blood cells contain abnormal hemoglobin known as hemoglobin S (Hb S). Hemoglobin is the material in red blood cells that carries oxygen from the lungs to the rest of the body. The abnormal hemoglobin has a tendency to aggregate, especially in parts of the body where oxygen content is low. This aggregation causes the red blood cells to form a sickle shape, which gives the disease its name.

Sickle cell anemia is caused by a mutation in the DNA (deoxyribonucleic acid) that codes for beta-globin, one of the proteins that makes up hemoglobin. More than 50,000 persons in the United States have sickle cell anemia. The disease is most common among African-Americans, but it is also seen among persons of Mediterranean, Caribbean, South and Central American, Arabian, and East Indian ancestry.

Sickle cell anemia is a hereditary disease. Patients inherit the abnormal gene from both their mother and their father; therefore their bodies can make only Hb S. The parents of patients with sickle cell anemia may have either sickle cell disease or sickle cell trait. Persons with sickle cell trait have one sickle cell gene and one normal beta-globin gene. They can make both Hb S and normal hemoglobin (Hb A). Persons with sickle cell trait are healthy but can have children with sickle cell anemia.

Sickle cell anemia is diagnosed by means of a blood test to determine that the red blood cells form a sickle shape. The blood test is followed by a more detailed examination of the blood to determine the presence of Hb S, Hb A, or any other abnormal hemoglobin.

A few patients with sickle cell disease have been cured with bone marrow transplantation from a brother or sister. However, this treatment remains highly experimental.

Sickle cell anemia is characterized by acute episodes of illness, known as crises. The most common type of crisis is a vasoocclusive or painful crisis; it is believed to be caused by blockage of blood vessels by sickled red blood cells. Patients experience severe pain, usually in the bones, and may have a fever. Symptoms usually last several days but may persist for more than a week.

Sickle cell anemia can affect every organ of the body, leading to complications such as kidney disease, eye disease, chronic hip or shoulder pain, heart disease, and leg ulcers. Sickling of red blood cells in the blood vessels of the brain may lead to strokes. Men with sickle cell anemia may have priapism, that is, a persistent, unwanted erection. Sickling in the spleen causes the organ to become inactive, making patients with sickle cell anemia prone to infections. Some of the more common infections are osteomyelitis (bone infection) and pneumonia.

Patients with sickle cell anemia may have a serious lung disorder known as acute chest syndrome. This syndrome is believed to be caused by a combination of sickling in the blood vessels of the lung and ribs and presence of pneumonia. Patients with sickle cell anemia also may experience a type of crisis known as aplastic crisis, in which the bone marrow temporarily stops making red blood cells. This type of crisis is usually associated with an infection (especially with the organism parvovirus B19) and can lead to severe anemia.

It is safe for patients with sickle cell anemia to travel in pressurized aircraft. However, travel in nonpressurized aircraft at high altitudes may trigger a crisis.

Treatment of sickle cell crisis involves controlling the pain. Mild crises can be managed with oral medications, which may or may not be narcotics. More severe pain crises may necessitate use of narcotics administered by means of intramuscular or intravenous injection. Fluids are given to prevent dehydration. Severe complications of sickle cell disease, such as stroke or acute chest syndrome, may be managed by means of exchange transfusion, which involves removing the patient's abnormal red blood cells and replacing them with normal red blood cells.

Hydroxyurea is a chemotherapeutic drug that appears to decrease the frequency of pain crises among patients with sickle cell anemia. Some patients with severe symptoms of sickle cell anemia may be treated with this drug.

Narcotic pain medications can cause drowsiness and constipation. Aspirin and nonsteroidal antiinflammatory drugs (NSAIDs), such as ibuprofen, can cause stomach pain and platelet abnormalities (platelets are blood cells that help form clots). Hydroxyurea can cause a decrease in all blood cell counts: red blood cells, white blood cells, and platelets. A low red blood cell count (anemia) can cause fatigue and shortness of breath. A low white blood cell count (neutropenia) can increase susceptibility to infection. A low platelet count (thrombocytopenia) can lead to easy bruising or bleeding.

Use of narcotics can lead to physical dependence and symptoms of withdrawal if the drug is stopped too quickly. However, true addiction (a psychologic need for the drug) is rare. Overuse of aspirin or NSAIDs can cause stomach ulcers and kidney disease. Overuse of acetaminophen (e.g., Tylenol) may produce liver damage. Hydroxyurea can cause fetal abnormalities; therefore patients should not become pregnant or father a child while taking it.

Children with sickle cell anemia generally receive prophylactic penicillin to prevent bacterial infection. Many sickle cell crises may be managed at home with oral pain medications, hydration, and rest.

• Take a daily folate supplement.
• Drink plenty of fluids to avoid dehydration, especially if you begin to have a painful crisis.
• Eat a healthy diet that contains green, leafy vegetables, which are high in folate.
• Participate in mild to moderate exercise as tolerated but be careful to rest if you feel tired and drink fluids after exertion.
• Dress warmly and avoid exposure to cold if possible; cold temperatures may trigger a crisis.
• Inform the surgeon or dentist that you have sickle cell anemia if you are undergoing elective surgical or dental procedures.
• Consider genetic counseling to determine your risk for having an affected child.
• Undergo prenatal care with both your obstetrician and your primary care physician. Although you may have a more complicated pregnancy than women without sickle cell disease, your likelihood of delivering a healthy baby is excellent.

• Do not overuse pain medications.
• Avoid excessive consumption of alcohol.
• Avoid overexertion.
• Avoid swimming in cold water, which may trigger a crisis.

• If you have a fever, shortness of breath, severe abdominal pain, priapism, neurologic symptoms (such as weakness on one side of your body or difficulty speaking), or a painful crisis that does not respond to management at home.

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