Inheritance and Genetics of SCID

SCID Genetics: Book Excerpts

• Immune Deficiency - genetics - Immune Deficiency
• Severe Combined Immunodeficiency - genetics - Severe Combined Immunodeficiency

SCID: Genetics Information

Genetics of SCID: All forms of SCID are inherited, with as many as half of SCID cases linked to the X chromosome, passed on by the mother. X-linked SCID results from a mutation in the interleukin 2 receptor gamma (IL2RG) gene which produces the common gamma chain subunit, a component of several IL receptors. IL2RG activates an important signalling molecule, JAK3. A mutation in JAK3, located on chromosome 19, can also result in SCID. Defective IL receptors and IL receptor pathways prevent the proper development of T-lymphocytes that play a key role in identifying invading agents as well as activating and regulating other cells of the immune system.

In another form of SCID, there is a lack of the enzyme adenosine deaminase (ADA), coded for by a gene on chromosome 20. This means that the substrates for this enzyme accumulate in cells. Immature lymphoid cells of the immune system are particularly sensitive to the toxic effects of these unused substrates, so fail to reach maturity. As a result, the immune system of the afflicted individual is severely compromised or completely lacking. (Source: Genes and Disease by the National Center for Biotechnology)

About inheritance and genetics:

Inheritance of SCID refers to whether the condition is inherited from your parents or "runs" in families. The level of inheritance of a condition depends on how important genetics are to the disease. Strongly genetic diseases are usually inherited, partially genetic diseases are sometimes inherited, and non-genetic diseases are not inherited. For general information, see Introduction to Genetics.

 » Next page: Treatments for SCID

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