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The genetics of severe combined immunodeficiency explain more about this disorder and how it is inherited. This disorder is actually a group of disorders, all of which are very rare and inherited, that are related to the immune system. Patients with this disorder's immune system is defective resulting in them being more vulnerable to infections that are potentially deadly. The most common form of this disorder is inherited in an x-linked recessive pattern. Approximately one out of every 100,000 babies are born with this disorder.
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Genetics of this Disorder
The genetics of severe combined immunodeficiency reveals that mutations in the gene IL2RG on the X chromosome are the cause. Mutations in the SCIDX1 gene on the X chromosome causes the most common form of this disorder. Another type of this disorder occurs when a mutation on chromosome 20 occurs, resulting in an enzyme adenosine deaminase deficiency.
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Symptoms of this Disorder
When a baby exhibits any of the following symptoms persistently for a minimum of one year, she should be evaluated for this disorder or other types of immune deficiency syndromes. Such symptoms include:
- A minimum of eight ear infections
- Infections that cannot be cured using antibiotics for at least two months
- Infections that must be treated with intravenous antibiotics
- Persistent thrush in the throat or mouth
- A minimum of two cases of pneumonia
- Failure to grow naturally or gain weight
- Deep-seated infections, such as an abscess in the liver or pneumonia affecting an entire lung
- Having a family history of infection-related infant deaths or immune deficiency
If the above symptoms are present, it is crucial that they are quickly evaluated. Those who are not diagnosed early enough often do not live past two years of age. This condition can be diagnosed before the baby is even born through procedures known as amniocentesis and chorionic villus sampling.
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Treating this Disorder
The most effective treatment for this disorder in a stem cell transplant of blood-forming stem cells that are obtained from a healthy person's bone marrow. The greatest chance for a cure comes from a bone marrow transplant that comes from a tissue-matched brother or sister. Donor transplants from unrelated donors or parents may also be done, but are less effective. When a transplant is performed within the patient's first three months of life, there is the best chance for a high success rate. Gene therapy may also be beneficial. This therapy would inject healthy copies of a gene, to compensate for the faulty gene, into the patient's bone marrow stem cells.
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National Human Genome Research Institute. (2010). Learning About Severe Combined Immunodeficiency. Retrieved on September 12, 2010 from the National Human Genome Research Institute: http://www.genome.gov/13014325
The University of Utah Genetic Science Learning Center. (2010). Severe Combined Immunodeficiency. Retrieved on September 12, 2010 from The University of Utah Genetic Science Learning Center: http://learn.genetics.utah.edu/content/disorders/whataregd/scid/