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Transcript of Science Project
"Learning About Severe Combined Immunodeficiency (SCID)." Learning About Severe Combined Immunodeficiency (SCID). N.p., n.d. Web. 23 Jan. 2013.
"X-linked Severe Combined Immunodeficiency." X-linked SCID. N.p., n.d. Web. 24 Jan. 2013
"New Gene Therapy Trials To Test Cure For Bubble Boy Syndrome | Singularity Hub." Singularity Hub. N.p., n.d. Web. 28 Jan. 2013 How does SCID or XSCID affect the body? Severe Combined Immunodeficiency Syndrome (SCID or XSCID)
By: Sophie and Samuel When someone has SCID or XSCID, the T cells that normally encourage other immune cells to act, do not act regularly. Neither do the B cells, whose job it is to fight sickness. Therefore, the person with the disorder cannot build up immunity either. They may catch the same sickness over and over, and they usually get sick frequently. What are some signs and Symptoms of SCID or XSCID? The normal symptoms of SCID or XSCID are repetitive or similar sicknesses in a short amount of time. This is why, in most cases, the child with the disease does not live past the age of two. Sometimes, a child with this disorder catches;
•Many ear infections (eight or more)
•More than a couple cases of pneumonia
•Infections that do not get better with medicine for two months or more
•Failure to gain weight or grow normally (failure to thrive)
•Infections that require antibiotic treatment to be given through the veins
•Deep-seated infections, such as pneumonia that affects an entire lung
•Persistent thrush which is abnormal amounts of yeast that form painful white spots in the mouth or throat
•A family history of SCID or XSCID or infant infections that have led to death How is SCID or XSCID diagnosed? When a child has had the symptoms and is brought in, blood test are taken, and if it is found that there are many fewer T cells than regular, and there are also few antibodies, the child is diagnosed positive because, even if the B cells produce antibodies, they will do little to counter the deficiency.
Sometimes, in an at-risk family, the fetus is tested before it is born by looking at the DNA of the fetus, but the test is expensive and not often used. How common is this disorder, in the U.S. and in the world? In the U.S. there is no overall record of how many children get diagnosed with SCID or XSCID each year, but the best estimate is am amount of cases somewhere around 40-100, which means that SCID and XSCID are rare conditions. unfortunately, there may be more cases, as some go undiagnosed.
In the world, there are also a low number of cases, with one child being affected out of 100,000 children.
Sometimes, this is called Bubble Boy Syndrome, as people affected by this would live in plastic bubbles so no germs would touch them. What genetic defect causes SCID or XSCID? When the IL2RG gene is mutated, it stops an important function. Normally, it would produce an essential protein for the immune system. Not receiving this protein stops lymphocytes from growing and functioning properly. Instead of protecting against possible sicknesses, producing antibodies, and regulating the immune system, the lymphocytes malfunction, and the affected person is unable to destroy sicknesses. How does this genetic abnormality specifically cause SCID or XSCID?
Severe combined immunodeficiency, or SCID, is a term applied to a group of inherited disorders characterized by defects in both T and B cell responses, hence the term "combined." The most common type of SCID is called XSCID because the mutated gene, which normally produces a receptor for activation signals on immune cells, is located on the X chromosome. Another form of SCID is caused by a deficiency of the enzyme adenosine deaminase (ADA), normally produced by a gene on chromosome 20. How is SCID or XSCID inherited? Are there any screening tests to detect the gene for this disorder before someone develops the symptoms? Is there a way to tell whether someone is a carrier?
Early diagnosis of SCID is rare because doctors do not routinely count each type of white blood cell in newborns. As a result, the average age at which babies are diagnosed with SCID is just over six months, usually because of recurrent infections (see below) and failure to thrive. Blood tests for SCID typically reveal significantly lower-than-normal levels of T cells and a lack of germ-fighting antibodies. Even if B cells are present in the blood of SCID patients, they do a poor job of producing antibodies. Low antibody levels and lack of specific antibodies after vaccination or a natural infection are characteristic features of SCID. How is it treated? The most effective treatment for SCID is transplantation of blood-forming stem cells from the bone marrow of a healthy person. Bone marrow stem cells can live for a long time by renewing themselves as needed and also can produce a continuous supply of healthy immune cells. A bone marrow transplant from a tissue-matched sister or brother offers the greatest chance for curing SCID. However, most patients do not have a matched sibling donor, so transplants from a parent or unrelated matched donor are often performed. These latter types of transplant succeed less often than do transplants from a matched, related donor. All transplants done in the first three months of life have the highest success rate. If the parents of a child are both dormant carriers, the child has a fifty percent chance of inheriting the disease. They also have a twenty-five percent chance of being a dormant carrier, and a twenty-five percent chance of being SCID or XSCID free, not inheriting the disease or carrying it. Any Questions???