Types of Severe Combined Immunodeficiency

More than a dozen genes have been implicated in SCID.

Source: NIAID (NIH)1

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Back to: « Severe Combined Immunodeficiency

Back to: « Combined Immunodeficiency

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Most often, SCID is inherited in an autosomal recessive pattern, in which both copies of a particular gene—one inherited from the mother and one from the father—contain defects. The best-known form of autosomal recessive SCID is caused by adenosine deaminase (ADA) deficiency, in which infants lack the ADA enzyme necessary for T-cell survival.

X-linked SCID, which is caused by mutations in a gene on the X chromosome, primarily affects male infants. Boys with this type of SCID have lymphocytes that grow and develop abnormally. As a consequence, they have low numbers of T cells and natural killer cells, and their B cells do not function.

Source: NIAID (NIH)2

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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.

Source: NHGRI (NIH)3

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Types of this condition may include:4 Types of severe combined immunodeficiency:

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Types of this condition:5 Types of severe combined immunodeficiency:

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Types of this condition may include:6

Types of Severe Combined Immunodeficiency:

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Types may include:7

Category of Severe Combined Immunodeficiency

Condition is a type of:

  • Combined Immunodeficiency

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    1. Source: NIAID (NIH): niaid.nih.gov/ diseases-conditions/ severe-combined-immunodeficiency-scid
    2. Source: NIAID (NIH): niaid.nih.gov/ diseases-conditions/ scid-causes
    3. Source: NHGRI (NIH): genome.gov/ 13014325/ learning-about-severe-combined-immunodeficiency-scid/ 
    4. Source: Disease Ontology
    5. Source: Monarch Initiative
    6. Source: NCI Thesaurus
    7. Source: MeSH (U.S. National Library of Medicine)

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