Severe+combined+immunodeficiency+(SCID)



** THE IMMUNE SYSTEM ** The immune system is one of the 7 functioning systems of the human body. Its job is to protect the body against infections and diseases. It is made up of organs, tissues, cells, cell products and proteins that works together to defend the body from any organisms or chemicals that may attack it such as parasites, virus, bacteria, fungi, toxins, carcinogen, pollution or germs. When any harm or any foreign antigen comes into the body, the immune system does its best to destroy it. When the body is strong, the immune system is successful in protecting itself, yet, in few cases, when a large part of the system is not working well disease takes place and medical care is needed. 1 The main “workers” of the immune systems are white cells. These develop in the bone marrow as stem cells. They can belong to any of the four different cell families:

B-lymphocytes – B cells T-lymphocytes – T cells NK-lymphocytes Phagocytes 1 ** What is SCID? ** Severe Combined Immunodeficiency or more commonly known as SCID is the most severe of all types of Primary Immune Deficiency diseases. 1 Also talked about as “bubble boy disease” it comprises a group of congenital (inherited) problems in genes that result in a defect in the B and T lymphocytes (the specialized white blood cells that protect the body from infection – the term combined is used because this disease presents defects in 2 lymphocytes). T cells combat infections by viruses and fungi and they also encourage other immune cells to respond when needed. B cells produce antibodies (which attack foreign substances) and antigens (which “mark” the invading fungi, bacteria and viruses, for other cells to attack them). An organism with defective T and B cells will present no or very little response to infections. 3 There are ten different forms of SCID. 1

** XSCID ** The most common type (almost 50% of cases) of SCID is the XSCID, given this name due to the fact that it is caused by a defect in the X chromosome where a receptor to activate responses in immune cells is located. This type of SCID appears mainly in male babies since males have only one X chromosome and, if it is defective, the disease appears. On the other hand, women have two X chromosomes, so if one is defective the other will supply its functions (thus, women can be carries of the disease and transmit it to their male children but very rarely present it). 3

** ADA ** If Chromosome 20 is defective a deficiency of the Adenosine deaminase enzyme will result. Without this enzyme the body is not able to breakdown toxic metabolites and when these accumulate they kill lymphocytes – thus causing SCID. This type of SCID can be controlled by permanent medical supervision and attention (intake of antibiotics and infusions of antibodies or injections of adenosine deaminase). 3

** SYMPTOMS ** SCID has no symptoms until the patient presents an infection (for example, ear infection, oral thrush, bronchitis, pneumonia, etc.) and generally it is not diagnosed until the infections of the patient (very young child) are so recurring that they affect its normal growth and development, making the doctor suspect a more serious problem. Then, when tests are done on the patient’s white cells, SCID can be detected. ** RESULTS ** If the defects are not corrected with the appropriate medical intervention, the child generally dies before reaching age two. 1  ** DIAGNOSIS ** As mentioned before, SCID is generally diagnosed when the patient is already suffering from it effects. Its diagnosis is done by counting the types of white blood cells in a patient’s blood; early diagnosis is infrequent (except in cases when there is a family history of this disease) because doctors do not routinely make blood tests in new born babies that include white cells counting and evaluation. SCID patients’ blood has lower than normal counting of T cells and a lack or very low number of antibodies. This test can be done in newborn babies, even though they appear healthy due to the fact that during the first moths of their lives antibodies received from their mothers protect babies. An early detection of SCID – before the baby catches an infection and suffers from its complications - can reduce costs of hospitalization and have a better recovery. Presently there is growing conscience that tests to detect SCID should be carried on all newborn babies. 3  ** TREATMENTS ** To the present, there are three types of available treatment. As most cells working in the immune system are produced in the bone marrow, when these cell-producing functions of the bone marrow are defective, an available cure is to perform a bone marrow transplant. This works by inserting into the patient bone marrow from a donor who has identical Human Leucocyte Antigen or HLA, which makes them be compatible. Frequently, to achieve success and the cure of the patient, various infusions of bone marrow may be needed. This procedure was first tried in 1868, but it was first successfully completed in 1973. Since the 80’s, the match of the donor does not have to be 100% HLA as it can be a ½ matched. This is the treatment that has been most used during the last 20 years. 1   After the Bone Marrow Transplantation procedure was created but not yet perfected, doctors were yet having a hard time to achieve an early diagnosis of SCID and, if a patient did not find a perfect HLA match (most commonly that of a brother or sister) he or she would die. The bubble procedure was introduced in 1971 when a women whose first child had had SCID and died from it, was pregnant once more, therefore presenting high risks of having another baby with SCID. To protect it in advance, right after birth the baby was placed into an “isolator crib” with special filtered air and into which only sterilized objects could be inserted. David, or most commonly know as “bubble boy”, grew inside the bubble and, later on, doctors proved he indeed had SCID. At this point a bone marrow transplant was to take place but, because no one in his family was an HLA match and there were no donors either, the transplant could not take place. Finally, “bubble boy” from an infection. 1
 * 1) ** Bone Marrow Transplantation **
 * 1) ** Bubbles **

Gene Therapy can be really useful in the cases when donors for bone marrow transplant are not found or when complications in this procedure take place. Gene therapy works by inserting a normal, healthy gene into the patient’s genome to be able to fix the defect that is the cause of the disease. This procedure is also currently used to cure cancer. 4  ** BENEFITS ** ** LIMITATIONS **
 * 1) ** Gene Therapy **
 * 1)  The research done to study SCID has been very important in the development of present knowledge of the immune system. This is crucial for the cure and detection of SCID but also for the cure and detection of other diseases or deficiencies of the immune system – something very important nowadays when, due to modern life our immune systems are constantly affected by external factors (pollution, contamination, etc.)
 * 2)  The lives of SCID patients and their treatments are a contribution to modern science – honorable purpose in life
 * 3)  SCID patients are generally better taken care off medically and frequently tested, thus an identification of any other diseases or mal functioning of their body, not related to SCID, is easier and takes place earlier than in normal healthy patients in whom the appearance of symptoms has to occur first.
 * 1)  A small child may be subjected to harsh treatments and even surgery since birth or since a very young age; this might affect him/her physically and even psychologically. 5
 * 2)  A kid who is SCID but has not been diagnosed will suffer constantly from various diseases that prevent him from having a normal healthy life and from growing normally (failure to thrive).
 * 3)  A child not treated generally dies before the age of 2.
 * 4)  A child diagnosed with SCID might be kept from the world (as in a bubble) or may have to wear a mask to avoid his/her catching diseases; this will lead to low social development and thus mal growth. 5
 * 5)  A person may be a carrier without knowing so and thus may pass the disease onto his/her children.
 * 6)  Treatment is expensive.
 * 7)  Since it is a very rare disease there are not many doctors dedicated to its study, detection and cure.

** ONE WORLD FACTORS ** // For more information look at this video: http://www.youtube.com/watch?v=G8LFatJZKTmedia type="youtube" key="G8LFatJZKT4" height="315" width="560" // ** BIBLIOGRAPHY **
 * 1) ** Social and economic ** : Since the lack of an early detection of SCID causes important monetary expenses (to the family and to society – social security organizations due to the costs of medical treatments), medical time and human suffering, due to the fact that the patient will suffer from frequent and recurring illnesses, failure to thrive and even death, an early detection of the disease is economically and socially important.
 * 2) ** Economic ** : The problem is that it would be expensive to introduce general testing for SCID for newborn babies with the techniques available nowadays (testing done individually and personally to each blood sample) – new mechanized techniques should be developed to make it less expensive. Since early detection results in a better response to treatment and saves the patient’s family and society from expenses and suffering, it is very important to develop a method of testing that is cheap, easy and fast.
 * 3) ** Ethical ** : There are certain procedures that allow the testing of a fetus in its mother’s womb and thus diagnose if it has any disease, including SCID. If SCID marks positive in a fetus there are two possible scenarios. The first is that the parents become aware of what is to come and thus take the necessary precautions and get in contact with the best doctors while learning about the disease and its treatments, to be able to provide a good care to the baby once it is born. Nevertheless, the option of abortion also appears once parents learn that their baby won’t be “normal”. There are many places in which this “therapeutic abortion” is allowed and this can bring up ethical issues that struggle around the fact of whether or not the fetus can be killed basically, whether or not this is morally or ethically correct or even legally correct (whether a fetus can be considered a human being with the right to live).
 * 1) Ballard, Barb. “About SCID.” //Severe Combined Immunodeficiency//. N.p., 2010. Web. 8 Mar. 2012. .
 * 2) “Definition of Severe Combined Immunodeficiency Disease.” //MedicineNet.com//. N.p., 2012. Web. 11 Mar. 2012. .
 * 3) “Learning about Severe Combined Immunodeficiency (SCID).” //National Human Genome Research Institute//. USA.gov, 3 Oct. 2011. Web. 11 Mar. 2012. .
 * 4) “Recombinant DNA Technology.” //Encyclopaedia Britannica Online School Edition//. Encyclopaedia Britannica, 8 Mar. 2012. Web. 11 Mar. 2012.
 * 5) “Severe Combined Immunodeficiency.” //KidsHealth//. The Nemours Foundation, 2012. Web. 11 Mar. 2012. .
 * 6) “Severe combined immunodeficiency.” NCBI. U.S. National Library of Medicine, n.d. Web. 11 Mar. 2012. .