Sickle-cell anemia is an inherited blood disorder that arises from a single amino acid substitution in one of the component proteins of hemoglobin. Hemoglobin being a protein that helps transport oxygen through the blood of vertebrates. It can cause serious and frequent infections, pain in the abdomen, back, and chest which could then potential damage major organs. The component protein, or globin, that contains the substitution is defective. Hemoglobin molecules constructed with such proteins have a tendency to stick to one another, forming strands of hemoglobin within the red blood cells. The cells that contain these strands become stiff and elongated, or, sickle shaped.
Genetics also have a hand in this. In fact, "A child who inherits the sickle cell trait from both parents--a 25% possibility if both parents are carriers--will develop sickle cell anemia"(World of Health, 2007). Sickle cell anemia is characterized by the formation of stiff and elongated red blood cells, called sickle cells. These cells have a decreased life span in comparison to normal red blood cells. Normal red blood cells survive for approximately 120 days in the bloodstream; sickle cells last only 10 to 12 days. As a result, the bloodstream is chronically short of red blood cells and the affected individual develops anemia. The sickle cells can create other complications. Due to their shape, they do not fit well through small blood vessels. As an aggravating factor, the outside surfaces of sickle cells may have altered chemical properties that increase the cell's stickiness. These sticky sickle cells are more likely to adhere to the inside surfaces of small blood vessels, as well as to other blood cells. As a result of the sickle cells' shape and stickiness, blockages occasionally form in small blood vessels. Such blockages prevent oxygenated blood from reaching areas where it is needed, causing extreme pain, as well as organ and tissue damage.
Normal hemoglobin is composed of a heme molecule and two pairs of proteins called globins. Humans have the genes to create six different types of globins--alpha, beta, gamma, delta, epsilon, and zeta (2007). A change, or mutation, in a gene can alter the formation or function of its product. In the case of sickle cell hemoglobin, the gene that carries the blueprint for beta-globin has a minute alteration that makes it different from the normal gene. This mutation affects a single nucleic acid along the entire DNA strand that makes up the beta-globin gene. Because of this seemingly slight mutation, called a point mutation, the finished beta-globin molecule has an amino acid substitution -- valine occupies the spot normally taken by glutamic acid. This substitution creates a hemoglobin molecule that does not function normally. Sickle cells die much more rapidly than normal red blood cells, and the body cannot create replacements fast enough. Anemia develops due to the chronic shortage of red blood cells. Further complications arise because sickle cells do not fit well through small blood vessels, and can become trapped. The trapped sickle cells form blockages that prevent oxygenated blood from reaching associated tissues and organs. Considerable pain results in addition to damage to the tissues and organs. This damage can lead to serious complications, including stroke and an impaired immune system.
Sickle cell anemia is suspected based on an individual's ethnic or racial background, and on the symptoms of anemia. A blood count reveals the anemia and the presence of sickle cells in blood samples is easily confirmed by microscopic examination. A sickle cell test can reveal the presence of the sickle cell trait. The sickle cell test involves mixing equal amounts of blood and a 2% solution of sodium bisulfite (2008). This will bring out the hemoglobin. If hemoglobin S is present, the red blood cells are transformed into the characteristic sickle shape. This transformation is observed with a microscope, and quantified by expressing the number of sickle cells per 1,000 cells as a percentage. The sickle cell test confirms that an individual has the sickle cell trait, but it does not provide a definitive diagnosis for sickle cell anemia. To confirm a diagnosis of the sickle cell trait or sickle cell anemia, another laboratory test called gel electrophoresis is performed. This test uses an electric field applied across a slab of gel-like material to separate protein molecules based on their size, shape, or electrical charge. The gel electrophoresis test is also used as a screening method for identifying the sickle cell trait in newborns.
Early identification of sickle cell anemia can prevent many problems. The highest death rates occur during the first year of life due to infection, aplastic anemia, and acute chest syndrome. If anticipated, steps can be taken to avert these crises. With regard to long-term treatment, prevention of complications remains a main goal. Sickle cell anemia cannot be cured--other than through a risky bone marrow transplant--but treatments are available for symptoms.
Blood transfusions are usually not given on a regular basis but are used to treat painful crises, severe anemia, and other emergencies. In some cases, such as treating spleen enlargement or preventing stroke from recurring, blood transfusions are given as a preventative measure. Regular blood transfusions have the potential to decrease formation of hemoglobin S, and reduce associated symptoms. However, regular blood transfusions introduce a set of complications, primarily iron loading, risk of infection, and sensitization to proteins in the transfused blood.
Bone marrow transplantation has been shown to cure sickle cell anemia in severely affected children. Indications for a bone marrow transplant are stroke, recurrent acute chest syndrome, and chronic unrelieved pain. Bone marrow transplants tend to be the most successful in children; adults have a higher rate of transplant rejection and other complications. The procedure requires a healthy donor whose marrow proteins match those of the recipient. Typically, siblings have the greatest likelihood of having matched marrow. Given this restriction, fewer than 20% of sickle cell anemia individuals may be candidates (2008). The percentage is reduced when factors such as general health and acceptable risk are considered. The procedure is risky for the recipient. There is approximately a 10% fatality rate associated with bone marrow transplants done for sickle cell anemia treatment. Survivors face potential long-term complications, such as infertility or development of cancer. Also, as a theoretical cure, you can apply gene therapy to the disease. It works by taking the infected gene out and replacing it with a fully functional correct gene. This would allow for correct function and disablement of the disease.