Alternative names:
anemia - sickle cell

Definition:
An inherited, chronic blood disease in which the red blood cells become crescent shaped and function abnormally

Causes, incidence, and risk factors:
Sickle cell anemia, which is caused by an abnormal type of hemoglobin (oxygen carrying pigment) called hemoglobin S, is inherited as an autosomal recessive trait. It occurs in people who have inherited hemoglobin S from both parents. If hemoglobin S is inherited from one parent, the offspring will have sickle cell trait and is usually without symptoms.

The disease occurs primarily in people of African Heritage, with 1 out of 400 African-Americans affected. The disease produces a chronic anemia which may become life-threatening when hemolytic crises (the breakdown of red blood cells) or aplastic crises (bone marrow fails to produce blood cells) occur. Repeated crises can lead to damage of the kidneys, lungs, bone and liver. Acute painful episodes caused by blocked blood vessels and damaged organs may occur and last hours to days affecting the bones of the back, the long bones, and the chest.

The overall incidence is 8 out of 100,000 people. The manifestations of this disease are a result of the fragility and inflexibility of the sickle red blood cells. When exposed to dehydration, infection, and low oxygen supply, these fragile red blood cells assume a crescent shape causing red blood cell destruction and thickening of the blood. Sickle cell anemia can affect many other body systems. Symptoms of this disease are most severe during periods called "sickle cell crisis." Although this disease is inherited and present at birth, symptoms usually don't occur until after 4 months of age.

Prevention:
Genetic counseling is recommended for carriers of the trait (about 1 in 12 African Americans has sickle cell trait). Prompt treatment of infections, adequate oxygenation, and maintaining normal hydration status may prevent sickling of red blood cells.

Prenatal diagnosis is now possible for couples at risk of producing a child with sickle cell anemia.

Symptoms:
 family history of sickle cell anemia
 fatigue
 breathlessness
 delayed growth and puberty
 susceptibility to infections
 ulcers on the lower legs (in adolescents and adults)
 jaundice
 bone pain
 attacks of abdominal pain
 weakness
 joint pain
 fever
 vomiting
Additional symptoms that may be associated with this disease:
 urine, bloody (hematuria)
 urination, excessive volume
 thirst, excessive
 penis pain
 priapism
 decreased fertility
 chest pain

Signs and tests:
 CBC
 hemoglobin S screening test
 hemoglobin electrophoresis
 sickle cell test
This disease may also alter the results of the following tests:
 urinary casts
 TIBC
 peripheral smear
 hemoglobin; serum
 ESR
 bilirubin

Treatment:
No cure is available for the disease. The objective of therapy is the comprehensive management and control of symptoms relating to crises. Bed rest to minimize energy expenditure and oxygen requirements during a crisis is recommended. Low oxygen levels result in acidosis which causes sickling.

Folic acid supplementation is a continuous therapy. Analgesics and adequate hydration are provided for acute, painful episodes. Blood transfusions may be given for aplastic or hemolytic crises, but should not be given routinely. A pneumococcal vaccine is given to prevent overwhelming infection in patients who have had a splenectomy. Electrolyte replacement is important, and hydration to dilute the blood is done via intravenous or oral fluid therapy.

Research is currently being done on a compound called hydroxyurea, which can induce some patients to produce a more normal blood protein and at least postpone sickle-cell attacks.

Parents should encourage their children to lead normal lives, but in order to decrease the occurrence of sickle cell crises, the following precautions should be considered:
A. To prevent tissue deoxygenation:
1. avoid strenuous physical activity, especially if the spleen is enlarged.
2. avoid emotional stress
3. avoid environments of low oxygen content (high-altitudes, non-pressurized airplane flights)
4. avoid known sources of infection
B. To promote hydration:
1. recognize signs of dehydration
2. avoid excess exposure to the sun
3. provide access to fluids at home and when away from home
C. To avoid sources of infection:
1. Keep child properly immunized as recommended by the health care provider.
2. Consider having the