Overview Of Sickle Cell Diseases Biology Essay


What is sickle cell disease? According to the National Human Genome Research Institute, "it is the most common inherited blood disorder in the Unites States." An estimated 80,000 Americans are currently living with sickle cell disease. Sickle cell has been known to affect mostly people of African American descent. Approximately one in 12 African Americans and one in 100 Hispanic Americans have the sickle cell trait, making them carriers of the disease ("Learning About").

Sickle cell is caused by a mutation in the "hemoglobin-Beta gene located on chromosome 11" ("Learning About"). According to The University of Maryland Medical Center, a normal hemoglobin cell appears round and smooth which will allow for an easier passage through blood vessels, while sickle cell hemoglobin will be rigid and take the shape of a "sickle." This causes the cells to stick together, which makes it difficult for them to pass through blood vessels. When enough cells clump together, it blocks the passageway and prevents oxygen rich blood from passing through ("Blood Diseases"). According to William C. Shiel, medical author for MedicineNet.com, the sickled cells are fragile and susceptible to rupture (hemolysis) and decrease the number of red blood cells. When this occurs, it is called anemia, and the condition is named "sickle cell anemia" (Shiel). A normal hemoglobin cell will live about 120 days, whereas a sickle cell can generally only survive for about 10 to 20 days. This short life cycle diminishes the red blood cell supply, resulting in anemia ("Blood Diseases").

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People with the sickle cell trait are immune to malaria, so the mutation is thought to have originated in areas where malaria prevalent. Malaria is carried by mosquitoes and the sickle cell trait protects the person from becoming infected with malaria ("Blood Diseases"). Since malaria is most common in Africa, this would prove why most people with sickle cell disease are of African descent. For a child to be born with sickle cell, both of their parents must have the genetic mutation. If the child has one parent that passes on the mutation, they will not develop sickle cell but will carry the trait which means they are capable of passing it on to their children ("Blood Diseases"). There is a 25 percent chance that a child will have sickle cell disease if both of the parents have the mutation. Also, the sickle cell gene can still be passed onto children, even if the parent is just a carrier of the disease ("Learning About").

There are several different ways a person can be tested for and diagnosed with sickle cell. According to Shiel, a "sickle prep" involves the use of a microscope to identify abnormal cells. It tests a smear of blood using a special low-oxygen preparation (Shiel). In many states, it is routine procedure to take a blood test on a new born to test for sickle cell. If the parents wish to know if their child will have the disease before it is born, amniocentesis may be performed while the child is still in the womb (Shiel). A way to determine if a person is a carrier, a blood test called a hemoglobin electrophoresis is performed ("Blood Diseases"). Along with all of these tests, a doctor will need a complete medical history and need to perform a physical exam on the patient ("Blood Diseases"). This will help the doctor in determining whether a person has sickle cell or not.

A person with sickle cell disease will experience many different symptoms and have dangerous complications throughout their lifetime. Some of these include: anemia, pain crisis, acute chest syndrome, splenic sequestration, stroke, and jaundice. Other common problems associated with sickle cell disease can include: increased infections, leg ulcers, bone damage, early gallstones, kidney damage, and eye damage ("Blood Diseases"). Fatigue appears to be one of the most common symptoms associated with sickle cell. As stated earlier, the life cycle of a red blood cell in a person with sickle cell is only about 10 to 20 days which means the bone marrow has to work harder in order to produce more and more red blood cells to make up for the rapid loss. A more severe form of anemia can result from the complete halt of red blood cell production, and this is then called an "aplastic crisis." An aplastic crisis may be the result of a stomach virus or flu, which is usually not a major problem for a person without sickle cell (Shiel). A pain crisis is also a common occurrence among those with sickle cell disease. They can be described as "intermittent painful episodes that are the result of inadequate blood supply to the tissues" (Shiel). Also called "vasoocclusive crises," they occur when the sickled cells clump together and get stuck in the blood vessel, blocking blood flow. A person having a pain crisis may experience pain anywhere, but the most likely places for it to occur are the chest, arms, and legs. Also associated with pain crises is dactylitis. Dactylitis is the painful swelling of the fingers and toes and is usually present in children under the age of three ("Blood Diseases").

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Acute chest syndrome is another symptom of sickle cell disease. It is considered a medical emergency and should not be taken lightly since it can be fatal. It consists of chest pain, fever, tachypnea, leukocytosis, and pulmonary infiltrates (Distenfeld). Acute chest syndrome will usually occur when the person already has an infection, fever, or is dehydrated. If a person has recurrent bouts of acute chest syndrome, in time, it can lead to permanent damage of the lungs ("Blood Diseases"). The spleen plays a large role in removing the sickled cells from the person's body. If the process of removing these cells occurs too quickly, splenic sequestration will result. Splenic sequestration is when large amounts of blood develop inside the spleen, causing it to become enlarged. A person experiencing splenic sequestration may develop shock and lose consciousness, and if not treated almost immediately, death may also occur (Shiel).

For a person living with sickle cell, leg ulcers can be a painful problem to have to deal with. A leg ulcer forms from minor injuries to the skin on the legs. Since sickle cell causes very poor circulation, the healing becomes delayed and infection sets in (Distenfeld). In adults, the ulcers will most commonly occur above the ankles and down the sides of the lower legs. Some may become so severe that they will cover the entire leg and resist treatment. Some ulcers can be so resistant that skin grafting must be done (Shiel). Another common problem associated with sickle cell is death of a part of a bone, or aseptic necrosis. This occurs as a result of poor oxygen supply to the bone. The most common sites for bone death to occur include the bones of the thighs, legs, and arms. Aseptic necrosis can cause permanent damage in some cases and a total joint replacement may be necessary (Shiel).

A person with sickle cell has a shorter life expectancy than a person without the disease. Until the discovery of new drugs and treatments, most people were not expected to live past their childhood years. "Today, half of sickle cell patients live beyond 50 years" ("Learning About"). The discovery of successful drug treatments and therapies has given people with sickle cell the chance to live a much longer life. As of now, the only absolute cure for sickle cell is a bone marrow transplant. In order for this to be successful, the person must have a sibling that is genetically compatible and is also willing to participate in the transplant. The problem with this is that only a very small percent of people with sickle cell will have a compatible donor and the procedure can be quite risky ("Learning About"). One new drug that can greatly benefit sickle cell patients is hydroxyurea. "Hydroxyurea inhibits ribonucleotide reductase, blocking DNA synthesis and cell division" ("Management"). It also improves fetal hemoglobin by creating more red blood cells ("Management"). The National Institutes of Health reported that sickle cell patients taking hydroxyurea had an increased life span. "Over 2 ½ years, the drug resulted in an almost 50 percent reduction in the number of painful crises and episodes of chest syndrome" ("Hydroxyurea"). Hydroxyurea seems to be a good drug for a person with sickle cell to take in order to control their symptoms and to prolong life.

One development in the science world in regard to sickle cell is the use of stem cells to cure mice of the disease. Researchers had been studying the disease in the mice and eventually figured out how to create stem cells from the skin cells of the mice. The scientists use many different techniques to turn the skin cells into what they call "induced pluripotent stem," or iPS, cells. The mice are then injected with their new, clean cells which will then begin producing new blood cells in the bones. The scientists studied the mice and found that their new stem cells had cured the mice of sickle cell by producing blood cells that were free of the disease ("Scientists"). This sort of experiment has not been tested on humans, but shows hope that it may one day work for the sufferers of sickle cell. This would be a great treatment because the stem cells would come directly from the person, not from embryonic stem cells which most people are opposed to.

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Even though a person living with sickle cell has a shorter life span than those without the disease, there are medications and therapies that can help prolong their life and allow them to live much longer than expected years ago. To manage their symptoms and complications, a person with sickle cell may take pain medications, have blood transfusions, and take penicillin, folic acid, or hydroxyurea ("Blood Diseases"). All of these are useful in prolonging a sickle cell patient's life. Even though the medications and therapies do benefit the person, death is still likely to occur. This is due mostly to bacterial infections, stroke, bleeding in the brain, and kidney, heart, or liver failure (Shiel). Knowing this, it is extremely important for a person with sickle cell to recognize even the smallest symptom, as it could result in death if left untreated.

Sickle cell disease is an inherited blood disease that becomes a lifelong battle for the person living with it. The many different and painful symptoms associated with sickle cell causes the person to have a different lifestyle than everyone else and causes them to have to visit their doctor on a much more frequent basis than most people. Knowing that the smallest infection or sickness could make them deathly ill is a terrible thing to have to endure day to day. There are several different kinds of medicines and treatments; however that can reduce the person's symptoms while ultimately prolonging their life. Hopefully researchers will discover how to cure sickle cell as they did in the mice experiment and allow people battling the disease to be free of the sickness for good.