Sickle Cell Disease

Sickle Cell Disease The sickle cell disease is an inherited blood disorder that affects red blood cells. People with sickle cell have red blood cells that have mostly hemoglobin’s, Sometimes these red blood cells become sickle-shaped or crescent shaped and have trouble going through small blood vessels. When sickle-shaped cells block small blood vessels, less blood can get to that part of the body. Tissue that does not get a normal blood flow eventually becomes damaged. This is what causes the problems of sickle cell disease.

As to this day there is really no cure for sickle cell disease. Red blood cells take oxygen from the air we breathe into our lungs to all parts of the body. Oxygen is carried in red blood cells by a substance called hemoglobin (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.

Hemoglobin S and hemoglobin C are abnormal types of hemoglobin. Oxygen is carried in red blood cells by a substance called hemoglobin. The main hemoglobin in normal red blood cells is hemoglobin A. Normal red blood cells 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 get to 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 are several types of sickle cell disease. The most common are: Sickle Cell Anemia (SS), Sickle-Hemoglobin C Disease (SC) Sickle Beta-Plus Thalassemia and Sickle Beta-Zero Thalassemia. Sickle Cell trait (AS) is an inherited condition in which both hemoglobin A and S are made in the red blood cells, there are always more A than S. Sickle cell trait is not a type of sickle cell disease. People with sickle cell trait are generally healthy.

Sickle cell conditions are inherited from parents in much the same way as blood type, hair color and texture, eye color and other physical things. The types of hemoglobin a person makes in the red blood cells depend upon what hemoglobin genes the person inherits from his or her parents. Like most genes, hemoglobin genes are inherited in two sets..one from each parent (Ex. If one parent has Sickle Cell Anemia and the other is Normal, all of the children will have sickle cell trait. 4 If one parent has sickle cell anemia and the other has sickle cell trait, there is a 50% chance (or 1 out of 2) of having a baby with either sickle cell disease or sickle cell trait with each pregnancy, When both parents have sickle cell trait, they have a 25% chance (1 of 4) of having a baby with sickle cell disease with each pregnancy).

HOW DO YOU KNOW IF YOU HAVE THIS TRAIT A SIMPLE PAINLESS 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,). 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 (arms, legs, chest and abdomen), stroke and priapism (painful prolonged erection).

It also causes damage to most organs including the spleen, kidneys and liver. Damage to the spleen makes sickle cell disease patients, especially young children, easily overwhelmed by certain bacterial infections. 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. Promising Treatment Developments In search for a substance that can prevent red blood cells from sickling without causing harm to other parts of the body, hydroxyurea was found to reduce the frequency of severe pain, acute chest syndrome and the need for blood transfusions in adult patients with sickle cell disease.

Hydroxyurea is a well-known drug, however its use in sickle cell disease is relatively new and must be approached with caution. Short-term side effects must be carefully monitored and long-term effects are still unknown POTENTIAL SAVINGS FROM USE OF HYDROXYUREA Estimated total U.S. sickle cell patients 65,000. Percent with severe pain 3-5 times per year 5.2%. Estimated number with frequent severe pain 3,380. Assuming the average annual number of episodes 4. The total number of severe pain episodes in these patients 13,520. Assuming that 50% episodes result in hospitalization 6,760 . Assuming the average days of hospitalization 5 .

Estimated total number of hospital days for these patients 33,800. Assuming cost per day $800. Total hospitalization costs for these patients $27,040,000. Potential savings from use of hydroxyurea in these patients in one year $13,520,000. Estimates of sickle cell disease patients in the U.S. is now over 70,000. In the US there were approximately 65,000 African-Americans suffering from sickle-cell disease.

There were about 5,500 British sufferers. Worldwide, 100,000 babies are born with the disease annually. Sickle cell anemia results when a person inherits two genes for sickle hemoglobin, and is homozygous for the mutation. American-Africans are the most likly to develope sickle cell anemia. Hemoglobin is composed of two pairs of peptide chains: two alpha chains and two beta chains. Sickle hemoglobin results from a point mutation in the beta-globin gene. This single nucleotide change produces a single amino acid change: a glutamic acid at position 6 has been changed to a valine, according to the following schedule.

COOH CH – (CH2)2-COOH Glutamic acid / NH2 COOH CH3 | CH – CH-CH3 Valine / NH2 Glutamic acid is, as the name says, an acidic amino acid, which means it will have a negative charge under normal body conditions and thus likes to be surrounded by water molecules. Valine, on the other hand, is a neutral, or uncharged, amino acid. Under normal conditions it behaves like a hydrophobic, organic molecule and wants to hide from water. This difference makes the globin chains of hemoglobin fold differently, especially in the absence of oxygen. Normal hemoglobin just gives up its oxygen when it gets to the tissue that needs it, but it retains its shape.

Sickle hemoglobin, on the other hand, loses its oxygen, and becomes relatively insoluble. In the deoxygenated form, it forms into long arrays that come out the shape of the red cell and produce the characteristic sickling that characterizes the disease. The insolubility of deoxygenated (reduced) sickle hemoglobin is the basis of two rapid diagnostic laboratory tests for sickle cell anemia. Scientists recently have had some limited success in using genetic engineering techniques to get good copies of the beta globin gene into people with sickle cell anemia. If they can succeed in this endeavor, people with the disease may be cured but will still be able to pass the genes onto their offspring.

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