Term Paper: Sickle Cell Disease

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Sickle cell disease is a severely debilitating genetic disorder that has no real cure except the risky bone marrow transplantation. Pharmacological interventions are thus largely focused on symptomatic management and in reducing the discomfort and pain for the patient. The promise of gene therapy as a cure is not immediately imminent. The severe psychosocial issues associated with the disease makes vocational rehabilitation a very important part of the successful management of the disease. Providing proper counseling and supportive therapy is essential in order to improve the quality of life for the affected individual.

Sickle cell disease affects millions of people throughout the world. The disease is particularly prominent among the sub-Saharan African people with very high incidence rates. In the western and central African regions for example, almost 25% of people have sickle cell trait and 1 to 2% of babies are born with the disease. In Nigeria alone every year around 45,000 to 90,000 new born babies are identified with the condition. The disease is also common in south and Central American countries, Cuba, and in Mediterranean countries such as Greece, Turkey and Italy. In Asia, India and Saudi Arabia have a high incidence of the disease. In the Untied States sickle cell disease presents a big healthcare problem with more than 70,000 cases of the disease and with an average of 1000 new babies born every year with the condition. [CDC] More than two million people are thought to be genetically predisposed for the condition and carry the sickle cell trait. Of all the various ethnic groups in the Untied states, the African-American population seems to have a high predisposition for the condition with one in every 500 people being identified with the disease. One in twelve African-Americans carries the sickle cell trait. The next ethnic group at risk is the Hispanic population with an incidence rate of 1 in every 1000 to 1400 people. [CDC]a brief overview of the sickle cell disease, its treatment and the psychosocial implications would provide us with a better insight into this debilitating condition.

Sickle Cell Disease Etiology

Sickle cell disease refers to a group of genetic disorders that result in alteration of the hemoglobin structure and hence disruptions in the normal circulation mechanism resulting in symptoms that range from intense and intermittent pain, anemia, stroke, high risk for infections, to severe organ damage due to disrupted blood supply. This is an inherited disorder and those identified with sickle cell disease in its most common form, the sickle cell anemia (Hb SS), have inherited one sickle cell gene from each parent. It is also possible that a person would inherit one sickle cell gene from a parent and a different type of abnormal gene from another parent resulting in a different type of the disease known as hemoglobin S. thalassemia. People who have inherited on sickle cell gene from one parent and a normal gene from another parent have what is known as the sickle cell trait but not the sickle cell disease. Children born to such parents are at a greater risk of developing the condition. [Nemours Foundation]

Molecular studies show that the substitution of valine in place of the glutamic acid in the 6th position of the beta chain changes the structure of the resultant hemoglobin in such a way that it elongates the red blood cells into a sickle shape. [Allan Platt] Thus the usually doughnut shaped Red blood cells are contorted into elongated sickle shaped cells. Due to the contorted shapes the RBC's find it difficult to pass through the blood vessels resulting in blockages along narrow blood vessels. The result is severe pain due to blockage. Also, since the lack of blood supply implies a lack of oxygen, the cells of the organs that are affected are at risk of hypoxia resulting in organ damage. Further it is known that sickle cells have a lower life period compared to normal red blood cells. Usually RBC's live up to 120 days while sickle cells have a life period of between 10 to 20 days, which results in a condition known as anemia (lower red blood cell count). [Nemours Foundation]

Diagnosis

Sickle cell disease can be diagnosed by blood tests in both children and adults. Hemoglobin electrophoresis, isoelectric focusing and liquid chromatographic techniques are commonly used. Sometimes solubility testing methods are also used though they are not an appropriate testing method for babies. Presently, in the United States, screening babies for sickle cell disease has become routine, as the risk of mortality due to opportunistic infections is very high among babies with sickle cell anemia. A recent Study has proved that a prophylactic course of oral penicillin reduces the risk of pneumococcal sepsis in infants by 84% indicating the importance of infant screening. [Doris L. Wethers, 2000]

Pathophysiology

Sickle hemoglobin forms into stiff polymers upon deoxygenation, which deform normal red blood corpuscles causing vaso-occlusion or blood vessel blockage particularly in smaller blood vessels. Even in larger blood vessels the accumulation of sickle cells in the vascular endothelium results in slowing down of the blood flow. It is also observed that due to the relatively lower life period of sickle red cells there is usually a high count of white blood cells in patients with sickle cell anemia resulting in the production of harmful levels of cytokines. Also, high hemolysis observed among sickle cell patients causes additional cardiac strain due to the extra effort required in pumping blood. Cardiomegaly is a frequently observed coexistent condition among children with sickle cell disease. The overworked bone marrow also implies the requirement of additional calories for normal growth process.

Sometimes bone marrow may not be able to sufficiently compensate for the rapid loss of red cells and this results in severe anemia due to bone marrow aplasia. Not infrequently, people with sickle cell disease have enlarged spleen due to the trapping of the abnormal RBC's in the spleen in a condition known as Splenic sequestration crisis. This is of particular significance for children as the spleen is an important defensive organ as it filters bacteria and other harmful organisms. Splenic dysfunction due to the accumulation of sickle cells along its surface is a major concern for sickle cell patients. [Doris L. Wethers]

Treatment Methods

Pharmacological interventions are based on providing relief and in management of the symptoms and the complications. Typical interventions include antibiotics for fighting opportunistic infections, use of effective pain management therapy and providing psychosocial support for the patient. Sometimes in the case of severely anemic patients blood transfusions maybe necessary and in such cases care should be taken to control possible complications due to frequent blood transfusions. For example, iron overload is one real problem with blood transfusions as red blood corpuscles contain iron. Above normal limits, iron has toxic effects on vital organs such as the heart, liver and the kidney. Thus the management of iron overload is important for sickle cell patients receiving blood transfusions. [SCDAA] We will now look at the most important pharmacological interventions for sickle cell patients.

Hydroxyurea

This is one of the principal drugs used in the management of symptoms pertaining to sickle cell disease. The drug works by inducing production of fetal hemoglobin. Since fetal hemoglobin is known to prevent the formation of sickle cells, the drug increases the mean corpuscular volume of the red cells and minimizes the number of sickle cells in the blood stream. A 1995 NIH study of hydrocyurea on patients above 18 years of age showed promising results such as considerably reduced periods of painful crisis and a 50% reduction in episodes of acute chest syndrome. In the United States, the FDA has approved the drug in 1998 for the treatment of adult sickle cell disease patients. Also the NIH clinical study was based on homozygous patients only (sickle cell anemia) and future test results are awaited for data on the other varieties of the disease. [Harvard University]

Erythropoietin and Nitric Oxide

This is another drug, which is proven to be effective in symptomatic control. The drug action is similar to that of hydroxyurea and it works by increasing the fetal hemoglobin levels in the red blood cells of the patients. In the human body the kidneys synthesize erythropoietin in response to hypoxemia. Nitric oxide is well-known for its muscle relaxation properties and is used in treating conditions of respiratory distress and pulmonary hypertension. NO works by interfering with the polymerization of sickle hemoglobin. [Harvard University]

Bone Marrow Transplantation

Currently bone marrow transplant is the only option that promises total cure or significant reduction in symptoms of the disease. It is advisable for patients who manifest intense and frequent symptoms. Some early studies have shown that patients with fetal hemoglobin levels less than 8.6% express severe and frequent symptoms and such patients are ideal candidates for bone marrow transplantation. This criterion is generally accepted due to the potential complications of a transplant operation, which include transplant mortality rate of 15% and a 15% risk for graft vs. host… [END OF PREVIEW]

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Sickle Cell Disease.  (2008, February 13).  Retrieved June 17, 2019, from https://www.essaytown.com/subjects/paper/sickle-cell-disease/62844

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