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Disorder Category

an other newborn disorder



Absent or severely reduced number of T-cell Receptor Gene Excision Circles (TRECs), which are produced during normal T-cell maturation

Tested By

TREC test; PCR-based assay that detects the number of TRECs



Severe Combined Immunodeficiency

“Bubble Boy” disease

XSCID (X-linked recessive form)

ADA SCID (Adenosine deaminase deficiency SCID)


279.2, Combined immunity deficiency


Severe Combined Immunodeficiency (SCID) includes a group of rare but serious, and potentially fatal, inherited immune disorders in which T lymphocytes fail to develop and B lymphocytes are either absent or compromised. Impairment of both B and T cells leads to the term “combined.” Untreated patients develop life-threatening infections due to bacteria, viruses, and fungi. The screening test for T cell receptor excision circles (TRECs), a byproduct of normal T cell development, identifies SCID as well as certain related conditions with low T cells that result in less severe immunodeficiency.


Approximately 1 in 50,000


There are several types of SCID; the most common form is X-linked recessive, affecting only males, while other forms are autosomal recessive

Prenatal Testing

DNA testing or enzyme analysis by amniocentesis or CVS; only recommended if there is a family history of SCID

Clinical Characteristics

Babies with severe combined immunodeficiency (SCID) are at high-risk for life-threatening infections beginning in their first few months of life. Without treatment, individuals suffer frequent infections that result in rashes, diarrhea, increasing illness, complications, and often lead to death within the first year or two of life.

Depending on the type of SCID, treatment modalities include hematopoietic transplant (bone marrow or stem cell), gene therapy (currently an investigational treatment), or enzyme replacement (for ADA SCID). Infants who receive hematopoietic transplant to reconstitute the immune system prior to 3.5 months of age have a >95% chance of survival. Transplantation survival decreases to less than 80% after 3.5 months of age, usually because of complications resulting from infections.

Early signs of SCID include:
  • Frequent, severe infections caused by common bacteria or viruses, or opportunistic infections, such as Pneumocystis jirovecii
  • Infections that do not respond appropriately to antibiotic treatment
  • Diarrhea
  • Poor weight gain or growth (failure to thrive)
  • Persistant thrush (candidiasis, a fungal infection) in the mouth or throat
  • Infections from live viral vaccines (rotavirus, MMR, and varicella vaccines)
  • A severe eczematous rash from birth that does not respond to treatment, in addition to other signs above.

Follow-up on positive screening test

Full characterization of the immune system will include complete blood count with differential, lymphocyte subset enumeration of T, B and NK cells, antibody levels, lymphocyte proliferation to mitogens; molecular genetic testing for specific gene diagnosis. In some cases, chimerism studies are completed as some infants with SCID acquire maternal lymphocytes in utero.

Primary care management

Upon notification of the + screen

  • Contact the family to inform them of the newborn screening result. Point out that additional tests are required to determine whether the baby actually has an immune deficiency (roughly half of initially positive tests may result from other T-cell immunodeficiencies or be falsely positive).
  • Avoid exposing the patient to sick contacts pending completion of testing.
  • If the infant has any signs of illness, refer to a tertiary pediatric hospital right away for evaluation and potential administration of immune globulin and antibiotics.
  • If the infant requires transfusion of any blood product, be sure that only leukocyte -reduced, irradiated products that are negative for cytomegaolovirus (CMV) are used. There is a theoretical risk of transfer of CMV from breastmilk, although no cases have been reported through breastmilk transmission. Some treatment centers recommend stopping breastfeeding/breastmilk unless mother is known to be CMV-negative.
  • DO NOT give live attenuated rotavirus vaccine, which could cause infection and prolonged diarrhea in a baby with SCID. This vaccine is to be given only after an immunology specialist confirms that the baby’s immune system is normal.
  • Consult with a specialist in pediatric immunodeficiency diseases (consult with a pediatric allergist/immunologist and/or infectious diseases specialist) who will assist with further testing.
  • Provide the family with basic information about SCID and T-cell lymphopenia (see resource list).

If the diagnosis is confirmed

  • Report confirmatory findings to newborn screening program.
  • Educate the family regarding signs, symptoms, and the need for urgent care when the infant becomes ill.
  • Consult with a specialist in pediatric immunodeficiency diseases who will be able to assist the family with treatment options, most likely a bone marrow transplant.

Specialty Care Collaboration

Initial consultation and ongoing collaboration with specialists in pediatric immunodeficiency diseases, genetic counseling, and support services for the family.


Information & Support

For Professionals

ACT Sheet for SCID (ACMG)
Developed by the American College of Medical Genetics (ACMG), includes recommended responses to positive newborn screening test results, diagnostic evaluation, clinical expectations, and sources of additional information. See the ACMG ACT Sheets and Confirmatory Algorithms (link elsewhere on this page) for more info and sheets on other conditions.

Immune Deficiency Foundation - SCID
The Immune Deficiency Foundation is the national patient organization dedicated to improving the diagnosis, treatment and quality of life of persons with primary immunodeficiency diseases through advocacy, education and research.

SCID (GeneReviews)
Excellent reviews on X-linked SCID by Eric Allenspach, MD PhD, David Rawlings, MD and Andrew Scharenberg, MD including clinical description, differential, management, genetic counseling, molecular genetics, and a bibliography.

Genetics in Primary Care Institute (GPCI)
Increases collaboration in the care of children with known or suspected genetic disorders. Includes health supervision and management guidelines, and other useful resources; a collaboration among the Health Resources & Services Administration, the Maternal & Child Health Bureau, and the American Academy of Pediatrics.

For Parents and Patients


An Internet self-help support group and resource guide for families afflicted with SCID.

SCID, Angels for Life
Offers information and videos from families sharing their own experiences with SCID.


Baby's First Test - SCID
Baby's First Test is the nation's newborn screening education center for families and providers. This site provides information and resources about screening at the local, state, and national levels and serves as the Clearinghouse for newborn screening information. This is an objective resource dedicated to educating parents, health professionals, and the public about the newborn screening system. This site also provides many ways for people to connect and share their viewpoints and questions about newborn screening.

National Human Genome Research Institute – Learning About SCID
Genetics and Genomics for Patients and the Public covers everything from detailed information about genetic disorders, background on genetic and genomic science, the new science of pharmacogenomics, tools to create your own family health history and a list of online health resources.

Immune Deficiency Foundation – IDF SCID Newborn Screening Campaign
IDF wants every state to include SCID Newborn Screening on their newborn screening panel immediately in order to save lives. To provide education and information about this issue, IDF has created awareness materials including the IDF SCID Newborn Screening blog, Parent Guides for Abnormal Screen and Diagnosis, the IDF SCID Newborn Screening Toolkit, and Advocacy Channel videos

X-Linked SCID (GHR)
From Genetics Home Reference, information for families about X-linked severe combined immunodeficiency, with a focus on the genetics of the condition and finding more information. (5036)


Genetics-related clinical services throughout the world can be found through Genetics Clinic Directory (GeneTests).

Newborn Screening Programs

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Pediatric Genetics

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Pediatric Hematology/Oncology

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Pediatric Immunology/Rheumatology

See all Pediatric Immunology/Rheumatology services providers (5) in our database.

Pediatric Infectious Disease

See all Pediatric Infectious Disease services providers (1) in our database.

For other services related to this condition, browse our Services categories or search our database.


Author: Nicole Tattersall, RN BSN - 11/2012
Reviewing Author: Karin Chen, MD - 5/2013
Content Last Updated: 6/2013