Severe immunodeficiency disorder
By: Ethan and Dawsen
Molecular
What chromosomes are involved?
- This disorder is located on the X chromosome, it is X-Linked recessive.
- Another form of SCID is caused by a defficiency of the ensyme adenosine deaminase (ADA), which is produced by a gene on chromosome 20.
- Males are more susceptible to this disorder (X-linked)
- An X-linked form of SCID (XSCID) was also found in basset hounds, and has similar characteristics to that found in humans.
- An autosomal recessive variant can be found in other animal species such as dogs, mice, and Arabian horses.
How is the DNA affected? What happens to the gene?
- A mutation/defect in the T and B cells (T cells notice foreign cells and tell the B cells to attack these foreign cells)
- Caused by mutations in the gene on the X chromosome called IL2RG.
- IL2RG is involved in creating the receptors on the surface of a lymphocyte.
- Because this gene is effected, the receptors don't recognize the foreign cells/matter and they aren't removed from the body.
- This gene is essentially turned off by the mutation*
Biochemical
How does this mutation affect the function/production of the protein and how does it affect the individual?
- This disorder effects the gene which is necessary in making receptors which direct lymphocytes to mature and mobilize in order to fight foreign matter.
- If the lymphocytes aren't directed to mature and move throughout the body, then they cannot protect the body from harmful external matter.
- This, in turn, then leaves the patient susceptible to viruses such as the common cold, or bacterial infections which wouldn't harm a healthy person.
How can it be spotted?
http://i.imgur.com/evbANd8.webm
What are symptoms to look for?
Most symptoms will be seen at a very early age, because the child may only live to the age of 3 if not treated.
- 8 or more ear infections at an early age.
- 2 or more cases of pneumonia.
- Infections that don't seem to have any effect from antibiotics.
- Failure to grow and thrive.
- A family history of the disease can also effect the likelihood that the child has the disorder well.
White blood cells attacking a parasite.
Organismal
What happens to the individual due to the genetic issues above? What are the symptoms?
- The affected individual is more susceptible to a large quantity of infections such as ear infections, lung infections, (pneumonia/bronchitis) and diarrhea.
- Since the individual is being attacked by so many infections, they have trouble growing.
- The child will also never gain weight and thrive, and will most likely pass before he/she is 3 years old.
What is the Treatment for SCID?
- The most common (and effective) treatment for SCID is stem-cell therapy.
- This therapy includes transplanting stem cells from the bone marrow of a healthy person.
- These stem-cells will continuously produce a supply of healthy cells and hopefully replace all the unhealthy cells.
- This procedure is even more effective if the Individual has siblings with matching tissues, and could even cure the SCID.
- If done within the first three months of life, the treatment will be more successful.
Statistics about SCID
- While there is no record of babies diagnosed with SCID, the best guess is about 40-100
- This is a very rare disease, which is good and bad; there aren't many people that get it, but when they do the treatments can be difficult.
- This disorder is only in babies, because if it isn't treated they die. It doesn't occur in anybody else.
- SCID is more common in male children due to males having only one X-chromosome, if it occurs in females, it is even more rare.
Did you know?
- SCID was best known from the news and even a movie created in the 80's about David, the Boy in the Bubble.
- David was born without a functional immune system, and was placed inside a plastic bubble to prevent him from being affected by bacteria.
- His "bubble" consisted of what looked to be an astronaut's space walk suit. He had a bubble dome around his head and had oxygen released through the suit.
Works Consulted
- Fundukian, Laurie J. The Gale Encyclopedia of Genetic Disorders. 3rd ed. Farmington Hills: Gale, 2010. Print.
- "Learning about Severe Combined Immunodeficiency (SCID)." Genome. National Human Genome Research Institute, n.d. Web. 3 Apr. 2016. <https://www.genome.gov/13014325#al-3>.
- "Severe Combined Immunodeficiency (SCID)." American Academy of Allergy, Asthma & Immunology. American Academy of Allergy, Asthma & Immunology, n.d. Web. 3 Apr. 2016. <https://www.aaaai.org/conditions-and-treatments/primary-immunodeficiency-disease/ severe-combined-immunodeficiency.aspx>.