Severe Combined Immunodeficiency (SCID)

Other Names

Severe Combined Immunodeficiency

“Bubble Boy” disease

XSCID (X-linked recessive form)

ADA SCID (Adenosine deaminase deficiency SCID)

Diagnosis Coding

D81.9, combined immunodeficiency, unspecified

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 (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 Testing after Positive Screen

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

SCID, X-Linked (OMIM)
Extensive review of literature that provides technical information on this genetic disorder; Online Mendelian Inheritance in Man site, hosted by Johns Hopkins University.

SCID (GeneReviews)
An expert-authored, peer-reviewed, current disease description that applies genetic testing to diagnosis and management information; U.S. National Library of Medicine.

Genetics in Primary Care Institute (AAP)
The goal of this site is to increase collaboration in the care of children with known or suspected genetic disorders. Includes health supervision guidelines and other useful resources; a collaboration among the Health Resources & Services Administration, the Maternal and Child Health Bureau, and the American Academy of Pediatrics.

SCID (Immune Deficiency Foundation)
A national organization dedicated to improving the diagnosis, treatment, and quality of life of people with primary immunodeficiency diseases.

Newborn Screening Information for Clinicians (NNSGRC)
Fact sheets, data reports, publications ,and information for clinicians about genetic screening that includes links to state genetic contacts; National Newborn Screening & Global Resource Center.

Utah Newborn Screening Program (UDOH)
Provides information about the program, related legislation, training for practices, and newborn conditions; Utah Department of Health.

For Parents and Patients


SCID Family Support
Support group and resource guide for families afflicted with SCID.

SCID: Angels for Life
Information and videos from families sharing their experiences with SCID.


X-Linked SCID (Genetics Home Reference)
Excellent, detailed review of condition for patients and families; sponsored by the U.S. National Library of Medicine.

SCID - Information for Parents (STAR-G)
A factsheet, written by a genetic counselor and reviewed by genetic specialists, for families who have received an initial diagnosis of a newborn disorder; Screening, Technology, and Research in Genetics.

Baby's First Test: SCID (Genetic Alliance)
Information about early signs, follow-up testing, treatment, causes, accessing care, and expected outcomes. Provides links to support services; supported by the U.S. Department of Health and Human Services.

Learning about SCID (National Human Genome Research Institute)
Answers to frequently asked questions about SCID and information about current clinical research.

SCID (Immune Deficiency Foundation)
A national organization dedicated to improving the diagnosis, treatment, and quality of life of people with primary immunodeficiency diseases.

Newborn Screening Information For Families (NNSGRC)
Information for families about genetic screening; links to support groups, advocacy groups, and state genetic contacts; newsletters; factsheets; data reports; and publications; National Newborn Screening and Global Resource Center.

Utah Parent Center
A non-profit organization that provides training, information, referral, and assistance to parents of children and youth with all disabilities including physical, mental, hearing, vision, learning, behavioral, and emotional. Staff consists primarily of parents of children and youth with disabilities.

Center for Parent Information and Resources (DOE)
A large resource library related to children with disabilities. Parent Centers in every state provide training to parents of children with disabilities. Lists local conferences, support groups, advocacy tips, and suggestions for finding schools and other local services; Department of Education, Office of Special Education.


ACT Sheet for SCID (ACMG) (PDF Document 279 KB)
Contains short-term recommendations for clinical follow-up of the newborn who has screened positive; American College of Medical Genetics.


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

Newborn Screening Programs

See all Newborn Screening Programs services providers (3) in our database.

Pediatric Genetics

See all Pediatric Genetics services providers (5) in our database.

Pediatric Hematology/Oncology

See all Pediatric Hematology/Oncology services providers (2) in our database.

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