Sickle cell anemia is a disease passed down through families in which red blood cells are an abnormal crescent shape. (Red blood cells are normally shaped like a disc.)

Sickle cell anemia is caused by an abnormal type of hemoglobin called hemoglobin S. Hemoglobin is a protein inside red blood cells that carries oxygen. Hemoglobin S, however, distorts the red blood cells' shape. The fragile, sickle-shaped cells deliver less oxygen to the body's tissues, and can break into pieces that disrupt blood flow.

Sickle cell anemia is inherited as an autosomal recessive trait. This means it occurs in someone who has inherited hemoglobin S from both parents. Sickle cell disease is much more common in certain ethnic groups, affecting approximately one out of every 500 African Americans. Someone who inherits hemoglobin S from one parent and normal hemoglobin (A) from the other parent will have sickle cell trait. Someone who inherits hemoglobin S from one parent and another type of abnormal hemoglobin from the other parent will have another form of sickle cell disease, such as thalassemia.

Although sickle cell disease is present at birth, symptoms usually don't occur until after 4 months of age. Sickle cell anemia may become life threatening. Blocked blood vessels and damaged organs can cause acute painful episodes, or "crises." There are several types of crises:

1. Hemolytic crisis occurs when damaged red blood cells break down
2. Splenic sequestration crisis is when the spleen enlarges and traps the blood cells
3. Aplastic crisis results when an infection causes the bone marrow to stop producing red blood cells

These painful crises, which occur in almost all patients at some point in their lives, can last hours to days, affecting the bones of the back, the long bones, and the chest. Some patients have one episode every few years, while others have many episodes per year. The crises can be severe enough to require admission to the hospital for pain control and intravenous fluids.

Repeated crises can cause damage to the kidneys, lungs, bones, eyes, and central nervous system.

Common symptoms include:

• Attacks of abdominal pain
• Bone pain
• Breathlessness
• Delayed growth and puberty
• Fatigue
• Fever
• Jaundice
• Paleness
• Rapid heart rate
• Susceptibility to infections
• Ulcers on the lower legs (in adolescents and adults)

The patient may also have:

• Bloody urine (hematuria)
• Chest pain
• Excessive thirst
• Frequent urination
• Painful erection (priapism; this occurs in 10 - 40% of men with the disease)
• Poor eyesight/blindness

Tests commonly performed to diagnose and monitor patients with sickle cell anemia include:

• Complete blood count (CBC)
• Hemoglobin electrophoresis
• Sickle cell test

Patients with sickle cell may have abnormal results on certain tests, as follows:

• Amount of oxygen in the blood may be decreased
• CT scan or MRI may show strokes in certain circumstances
• Elevated bilirubin
• High serum creatinine
• High serum potassium
• High white blood cell count
• Peripheral smear displays sickle cells
• Serum hemoglobin will be decreased
• Urinary casts or blood in the urine