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X-linked severe combined immunodeficiency

(also known as X-linked SCID)
Reviewed November 2005

What is X-linked SCID?

X-linked severe combined immunodeficiency (SCID) is an inherited disorder of the immune system that occurs almost exclusively in males. Boys with X-linked SCID are prone to recurrent and persistent infections caused by certain bacteria, viruses, and fungi. These infections can be very serious or life-threatening. The organisms that cause infection in people with X-linked SCID are described as opportunistic because they ordinarily do not cause illness in healthy people. Many infants with X-linked SCID experience chronic diarrhea and skin rashes, and grow more slowly than other children. Without treatment, affected males usually do not live beyond infancy.

How common is X-linked SCID?

X-linked SCID is the most common form of severe combined immunodeficiency. The exact incidence is unknown, but the condition probably affects at least 1 in 50,000 to 100,000 births.

What genes are related to X-linked SCID?

Mutations in the IL2RG gene cause X-linked severe combined immunodeficiency.

The IL2RG gene provides instructions for making a protein that is essential to immune system function. This protein is necessary for the growth and maturation of developing immune system cells called lymphocytes. Lymphocytes defend the body against potentially harmful invaders, make antibodies, and help regulate the entire immune system. Mutations in the IL2RG gene prevent these cells from developing and functioning normally. Without functional lymphocytes, the body is unable to fight off infections.

How do people inherit X-linked SCID?

This condition is inherited in an X-linked recessive pattern. A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a mutation must be present in both copies of the gene to cause the disorder; this situation occurs only rarely. Therefore, males are affected by X-linked recessive disorders much more frequently than females.

Where can I find information about treatment for X-linked SCID?

You may find information on treatment or management of X-linked SCID or some of its symptoms in the links below, particularly the links for Gene Reviews, MedlinePlus Encyclopedia, Educational resources, and Patient support.

Where can I find additional information about X-linked SCID?

You may find the following resources about X-linked SCID helpful. These materials are written for the general public.

  • MedlinePlus - Health information
    • Encyclopedia: Immunodeficiency Disorders (http://www.nlm.nih.gov/medlineplus/ency/article/000818.htm)
    • Health Topic: Immune System and Disorders (http://www.nlm.nih.gov/medlineplus/immunesystemanddisorders.html)
  • Additional NIH Resources - National Institutes of Health
    • Eunice Kennedy Shriver National Institute of Child Health and Human Development: Primary Immunodeficiency (http://www.nichd.nih.gov/publications/pubs/primary_immuno.cfm)
    • National Cancer Institute: Understanding the Immune System (http://www.cancer.gov/cancertopics/understandingcancer/immunesystem)
    • National Center for Biotechnology Information: Genes and Disease (http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=gnd.section.153)
    • National Human Genome Research Institute: Learning About Severe Combined Immunodeficiency (http://www.genome.gov/13014325)
  • Educational resources - Information pages
    • Centers for Disease Control and Prevention (http://www.cdc.gov/genomics/hugenet/factsheets/FS_IL2RG_ScidPid.htm)
    • Children's Hospital Boston (http://www.childrenshospital.org/az/Site1577/mainpageS1577P0.html)
    • Genetic Science Learning Center, University of Utah (http://learn.genetics.utah.edu/content/disorders/whataregd/scid/index.html)
    • Great Ormond Street Hospital for Children NHS Trust (UK) (http://www.gosh.nhs.uk/gosh_families/information_sheets/immunodeficiency_scid/immunodeficiency_scid_families.html)
    • KidsHealth from the Nemours Foundation (http://www.kidshealth.org/parent/medical/allergies/severe_immunodeficiency.html)
    • Madisons Foundation (http://www.madisonsfoundation.org/index.php/component/option,com_mpower/diseaseID,69/)
    • Merck Manual of Medical Information, Home Edition for Patients and Caregivers (http://www.merck.com/mmhe/sec16/ch184/ch184i.html)
    • National Marrow Donor Program: Severe Combined Immunodeficiency and Transplant (http://www.marrow.org/PATIENT/Undrstnd_Disease_Treat/Lrn_about_Disease/Immune_System/SCID_and_Tx/index.html)
    • Orphanet (http://www.orpha.net/consor/cgi-bin/OC_Exp.php?Lng=EN&Expert=276)
    • Swedish Information Center for Rare Diseases (http://www.socialstyrelsen.se/en/rarediseases/Severe+combined+immunodeficiency.htm)
  • Patient support - For patients and families
    • Immune Deficiency Foundation (http://www.primaryimmune.org/)
    • International Patient Organisation for Primary Immunodeficiencies (http://www.ipopi.org/)
    • National Organization for Rare Disorders (http://www.rarediseases.org/search/rdbdetail_abstract.html?disname=Severe+Combined+Immunodeficiency)
    • National Primary Immunodeficiency Resource Center (http://npi.jmfworld.org/)
    • Primary Immunodeficiency Association (UK) (http://www.pia.org.uk/)

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

  • Gene Reviews - Clinical summary (http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=x-scid)
  • Gene Tests - DNA tests ordered by healthcare professionals (http://www.genetests.org/query?testid=2401)
  • ClinicalTrials.gov - Linking patients to medical research (http://clinicaltrials.gov/search/condition=%22x-linked+severe+combined+immunodeficiency%22+OR+%22severe+combined+immunodeficiency%22)
  • PubMed - Recent literature (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?CMD=search&DB=PubMed&term=(Severe+Combined+Immunodeficiency[MAJR])+AND+((x-linked+severe+combined+immunodeficiency[TIAB])+OR+(scidx1[TIAB])+OR+(x-scid[TIAB])+OR+(xscid[TIAB]))+AND+english[la]+AND+human[mh]&orig_db=PubMed&filters=ON&pmfilter_EDatLimit=1800+Days)
  • OMIM - Genetic disorder catalog (http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=300400)

What other names do people use for X-linked SCID?

  • SCIDX1
  • XSCID
  • X-SCID

See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.

What if I still have specific questions about X-linked SCID?

  • See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.
  • Ask the Genetic and Rare Diseases Information Center (http://rarediseases.info.nih.gov/GARD/).
  • Submit your question to Ask the Geneticist (http://www.askthegen.org/).

What glossary definitions help with understanding X-linked SCID?

antibody ; bacteria ; B-cells ; cell ; chromosome ; chronic ; fungus ; gene ; immune system ; immunodeficiency ; incidence ; infection ; killer cells ; lymphocyte ; mutation ; natural killer cells ; protein ; recessive ; sex chromosomes ; T-cells ; virus ; X-linked recessive

You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://ghr.nlm.nih.gov/glossary).

References
  • Buckley RH. Molecular defects in human severe combined immunodeficiency and approaches to immune reconstitution. Annu Rev Immunol. 2004;22:625-55. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&dopt=Abstract&list_uids=15032591)
  • Chinen J, Puck JM. Successes and risks of gene therapy in primary immunodeficiencies. J Allergy Clin Immunol. 2004 Apr;113(4):595-603; quiz 604. Review. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&dopt=Abstract&list_uids=15100660)
  • Church AC. X-linked severe combined immunodeficiency. Hosp Med. 2002 Nov;63(11):676-80. Review. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&dopt=Abstract&list_uids=12474613)
  • Gene Review: X-Linked Severe Combined Immunodeficiency (http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=x-scid)
  • Gennery AR, Cant AJ. Diagnosis of severe combined immunodeficiency. J Clin Pathol. 2001 Mar;54(3):191-5. Review. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&dopt=Abstract&list_uids=11253129)
  • Huang H, Manton KG. Newborn screening for severe combined immunodeficiency (SCID): a review. Front Biosci. 2005 May 1;10:1024-39. Review. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&dopt=Abstract&list_uids=15769602)
  • Ochs, Hans D; Smith, Edvard; Puck, Jennifer; Primary immunodeficiency diseases : a molecular and genetic approach; New York : Oxford University Press, 1999. p99-110.

 

The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.

 
Reviewed: November 2005
Published: May 11, 2009