Sickle Cell Disease
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What is Sickle Cell Disease (SCD)?
Sickle cell disease is an inherited blood disorder that affects red blood cells. People with sickle cell disease have red blood cells that contain mostly hemoglobin S, an abnormal type of hemoglobin. Sometimes these red blood cells become sickle-shaped (crescent shaped) and have difficulty passing through small blood vessels. When sickle-shaped cells block small blood vessels, less blood can reach that part of the body. Tissue that does not receive a normal blood flow eventually becomes damaged. This is what causes the complications of sickle cell disease. There is currently no universal cure for sickle cell disease.
Hemoglobin is the main substance of the red blood cell. It helps red blood cells carry oxygen from the air in our lungs to all parts of the body. Normal red blood cells contain hemoglobin A. Normal red blood cells that contain hemoglobin A are soft and round and can squeeze through tiny blood tubes (vessels). Normally, red blood cells live for about 120 days before new ones replace them.
People with sickle cell conditions make a different form of hemoglobin A called hemoglobin S (S stands for sickle). Red blood cells containing mostly hemoglobin S do not live as long as normal red blood cells (normally about 16 days). They also become stiff, distorted in shape and have difficulty passing through the body’s small blood vessels. When sickle-shaped cells block small blood vessels, less blood can reach that part of the body. Parts of the body that don’t receive a normal blood flow eventually become damaged. This is what causes the complications of sickle cell disease although some individuals may be eligible for a curative bone marrow transplant.
Types of Sickle Cell Disease
There are several types of sickle cell disease. The most common are:
- Hemoglobin SS Disease, Hemoglobin SC Disease
- Sickle Beta-Plus Thalassemia
- Sickle Beta-Zero Thalassemia.
Complications & Treatment
Medical Problems
Sickle cells are destroyed rapidly in the body of people with the disease causing anemia, jaundice and the formation of gallstones.
The sickle cells also block the flow of blood through vessels resulting in lung tissue damage (acute chest syndrome), pain episodes (commonly in the arms, legs, chest and abdomen), stroke and priapism (painful prolonged and unwanted erection). It also causes damage to most organs including the spleen, kidneys, eyes and liver. Damage to the spleen makes sickle cell disease patients, especially young children, easily infected by certain bacterial. Therefore, any fever in someone with sickle cell disease must be taken very seriously.
Treatment
Health maintenance for patients with sickle cell disease starts with early diagnosis, preferably in the newborn period and includes penicillin prophylaxis, vaccination against pneumococcus bacteria and folic acid supplementation.
Treatment of complications often includes antibiotics, pain management, intravenous fluids, blood transfusion and surgery all backed by psychosocial support. Like all patients with chronic disease patients are best managed in a comprehensive multi-disciplinary program of care.
Blood Transfusions Blood transfusions help benefit sickle cell disease patients by reducing recurrent pain crises, risk of stroke and other complications. Because red blood cells contain iron, and there is no natural way for the body to eliminate it, patients who receive repeated blood transfusions can accumulate iron in the body until it reaches toxic levels. It is important to remove excess iron from the body, because it can gather in the heart, liver, and other organs and may lead to serious organ damage and even death. Treatments are available to eliminate iron overload (see below).
Hydroxyurea for treating Sickle Cell Disease A single randomized clinical trial of 299 patients with SCD demonstrated that compared to placebo, hydroxyurea was associated with lower annual rates of pain crises, pain episodes of acute chest syndrome and need for transfusions. Hydroxyurea was first approved by the FDA for SCD in 1998 and is now available for adults and children with sickle cell anemia.
Transfusional Iron Overload Patients with sickle-cell disease (SCD) receiving chronic transfusions of red blood cells are at risk of developing transfusional iron overload over time. Transfusional iron overload is characterized by an increase of labile plasma iron (i.e., non-transferrin bound iron) in the body, which can lead to functional impairment in vital organs. The organs that are at risk of damage due to iron overload include the liver, heart, pancreas, thyroid, pituitary gland, and other endocrine organs. Buildup of labile plasma iron in these organs can lead to hepatic cirrhosis, cardiomyopathy, diabetes mellitus, hypoparathyroidism, impaired growth, infertility, hypogonadism and even death. The body does not have a way to get rid of iron received from blood transfusions. An agent that chelates iron is therefore needed to get rid of excess iron in the body. There are two agents. One agent is given intravenously and the other is by mouth.
How will I know if I have Sickle Cell Disease or Trait?
A simple blood test, followed by a laboratory technique called Hemoglobin Electrophoresis, will determine the type of hemoglobin you have. When you pass an electric charge through a solution of hemoglobin, distinct hemoglobins move different distances, depending on their composition. This technique differentiates between normal hemoglobin (A), Sickle hemoglobin (S), and other different kinds of hemoglobin (such as C, D, E, etc.). It is important that the testing also includes a complete blood count with assessment of the mean corpuscular volume (MCV).
