Sickle Cell Anemia Bibliography


Sickle Cell Anemia Questions

logo-scdaa.jpgSickle Cell Anemia
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Laura M McCaul P Catherine Q Paige W
Inheritance
Sickle cell anemia is a hereditary disease that is caused by the recessive mutation S from both parents. If both parents carry the S mutation, there is a 25% chance the child will have the disease, 50% chance the child will not carry the disease, but will carry the sickle cell trait, and 25% chance the child will not get the disease, or carry the sickle cell trait. If only one parent carries this S mutation but is healthy, there is a 50% chance the child will carry the sickle cell trait, but not inherit the disease, and a 50% chance the child will not inherit the disease or have the trait.


B
S
B
BB
BS
S
BS
SS
Genotype: 25% BB 25% SS 50% BS Phenotype: 25% healthy 25% sickle cell anemic 50% carrier
B represents an HBB allele that is normal. S represents an HBB allele that is deformed, or HbS. Normal HBB alleles are dominant while mutated HbS alleles are recessive.


B
S
B
BB
BS
B
BB
BS
Genotype: 50% BB 50% BS Phenotype 50% healthy 50% carriers


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The gene HBB (hemoglobin beta) on chromosome 11 controls this disease. If both HBB alleles are regular, there will be no sickle cell anemia. However, if chromosome 11 has a mutation that causes an HBB allele to be HbS, it becomes a recessive sickle-cell allele. If one nucleotide on a normal HBB gene is substituted, the gene becomes HbS. The one substitution of a thymine where an adenine should be makes this switch. When thymine is incorrectly in the sequence, valine joins the chain instead of glutamine. Though it only affects that one amino acid in the protien, the protein tells the cell to make the wrong kind of hemoglobin.

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t11.jpg from Ornl.gov and Heartnet.edu



Characteristics and Symptoms
Sickle cell anemia affects every organ and every system of the human body. The characteristics of the disease are the shape and function of red blood cells is deformed. Normal blood cells can live up to 120 days. But, sickle cells are extremely fragile, and they only live up to about 10 or 20 days. Sickle cells become stiff, which makes it harder for them to move through the narrow blood vessels. The sickle cells can also become sticky, which causes the vessels to clump up into groups.



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From the National Heart Lung and Blood Institute


This causes blockage in the blood vessels. The blockage causes blood vessel damage, which can result in strokes, heart disease, and the symptoms of sickle cell anemia.
These symptoms are pain and swelling of hands and feet, decreased blood flow which can cause a slower development or growth, and delay of puberty in young children. It can also cause a person immune system to break down, and the healing of skin and organs can also be slowed down. Other symptoms can also be fatigue, paleness, and shortness of breath. Sickle Cell Anemia can also cause an increase in infections, leg ulcers, bone damage, early gallstones, kidney damage, loss of body water in urine, and eye damage.

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Also, sickle cells die quicker than other red blood cells, and the liver can not keep up with filtering them out. Bilirubin builds up in the dead cells that are not filtered out quick enough; it builds up in the system causing Jaundice. This causes the skin, eyes, and mouth to turn a yellowish color.
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This disease can also cause serious conditions like...
· Splenic sequestration or pooling, which is when the sickle cells get strapped in the spleen. This causes damage to the spleen, enlargement of the spleen, and can cause severe pain. Most people with sickle cell anemia have their spleens removed. If the spleen is left inside the body defective it may cause a major drop in hemoglobin in the body which can lead to death. So, it is suggested that the spleen be removed.
· There can also be sickling in the chest which can be very serious and even fatal. This is called Acute Chest Syndrome. It is caused when there is stress from infection or dehydration, and the blood cells begin to clump in the blood vessels in the lung. This causes a lack of oxygen flowing to the lungs. This syndrome can be mistaken for Pneumonia: fever, pain, and violent coughing. Multiple episodes of the syndrome can cause permanent damage to the lungs.
· It can also cause pain crisis or sickle crisis, which is when blood flow is blocked to one area. This causes pain and swelling. This can kill the surrounding tissue in the area because of lack of oxygen.
· It can also cause a person to have a stroke, which is when the major blood vessels that carry oxygen to the brain become blacked. Any lack of blood flow or oxygen to the brain can cause a stroke.


asssssdddddddddddddddTreatment

There is no cure for sickle cell anemia. Treatment for children starting at 2 months old to 5 years of age are treated with oral penicillin twice a day. This treatment is use to prevent pneumococcal infection . Pneumococcal infection is a bacteria that causes an infection in the brain and blood poisoning. This infection occurs before a child is 3 and 35% of children with sickle cell anemia die.
For infants born with fetal hemoglobin (HbF) they use the treatment hyfroxyurea. After birth the amount of HbF decreases quickly. Hyfroxyurea is taken by mouth once a day to increase the production of HbF, and by doing that it reduce sickling of the cells, and other major complications of the disease.
Another form of treatment that is more lifelong is blood transfusions. It is used to prevent complications, such as recurring strokes in children. It can be used to treat spleen enlargement in children before it gets too serious and life threatening.
For future treatment bone marrow transplants has shown to cure children. The risks of the transplant has been reduce, but there is still a high level of risk involved and a person’s only donor is a healthy sibling and only 18% of people with sickle cell anemia have a match.
Extra Facts
There are different forms of the disease: Hemoglibin SS, Hemoglobin Sc, and Hemoglobin Sb (Beta Thalassemia).