X-linked severe combined immunodeficiency: Difference between revisions
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{{Short description|A genetic disorder affecting the immune system}} | {{Short description|A genetic disorder affecting the immune system}} | ||
'''X-linked severe combined immunodeficiency''' (X-linked SCID) is a genetic disorder that severely affects the immune system, leading to a lack of functional [[T cells]] and [[natural killer cells]]. This condition is part of a group of disorders known as [[severe combined immunodeficiency]] (SCID), which are characterized by a severely compromised immune system. | '''X-linked severe combined immunodeficiency''' (X-linked SCID) is a genetic disorder that severely affects the immune system, leading to a lack of functional [[T cells]] and [[natural killer cells]]. This condition is part of a group of disorders known as [[severe combined immunodeficiency]] (SCID), which are characterized by a severely compromised immune system. | ||
Revision as of 04:27, 23 March 2025
A genetic disorder affecting the immune system
X-linked severe combined immunodeficiency (X-linked SCID) is a genetic disorder that severely affects the immune system, leading to a lack of functional T cells and natural killer cells. This condition is part of a group of disorders known as severe combined immunodeficiency (SCID), which are characterized by a severely compromised immune system.
Genetics
X-linked SCID is caused by mutations in the IL2RG gene, which is located on the X chromosome. The IL2RG gene encodes the common gamma chain (γc), a protein that is a component of several interleukin receptors, including those for interleukin-2, interleukin-4, interleukin-7, interleukin-9, interleukin-15, and interleukin-21. These interleukins are crucial for the development and function of immune cells.
Since the disorder is X-linked, it primarily affects males, who have only one X chromosome. Females, with two X chromosomes, are typically carriers and usually do not exhibit symptoms, although they can pass the mutated gene to their offspring.
Pathophysiology
The absence of a functional common gamma chain in X-linked SCID leads to a failure in the signaling pathways necessary for the development and maturation of T cells and natural killer cells. As a result, affected individuals have a severely compromised immune system, making them highly susceptible to infections.
Clinical Presentation
Infants with X-linked SCID typically present within the first few months of life with recurrent infections, failure to thrive, and chronic diarrhea. Common infections include those caused by opportunistic organisms such as Pneumocystis jirovecii, Candida albicans, and various viruses. Without treatment, these infections can be life-threatening.
Diagnosis
Diagnosis of X-linked SCID is often made through newborn screening programs that detect low levels of T-cell receptor excision circles (TRECs), which are byproducts of T-cell development. Confirmatory testing includes genetic testing to identify mutations in the IL2RG gene.
Treatment
The primary treatment for X-linked SCID is hematopoietic stem cell transplantation (HSCT), which can restore immune function if performed early in life. Gene therapy is an emerging treatment option that involves correcting the genetic defect in the patient's own hematopoietic stem cells.
Prognosis
With early diagnosis and treatment, individuals with X-linked SCID can have a significantly improved prognosis. However, without treatment, the condition is usually fatal within the first year of life due to overwhelming infections.
