Diagnosis guide
Severe combined immunodeficiency (SCID)
SCID is a group of genetic conditions that profoundly impair T-cell immunity. Other immune cells may also be affected, depending on the subtype. Newborn screening can identify a child before symptoms develop. Suspected SCID needs urgent specialist assessment and infection prevention directed by the care team. Donor transplantation is an established treatment for many forms; selected subtypes also have gene-therapy or enzyme-replacement options. The exact genetic cause matters. RAG1 and RAG2 variants, for example, can also cause less severe or later-onset immune disorders; not every variant causes classic SCID.
In short
- SCID is the name for a group of genetic conditions that badly weaken T cells, a key part of the immune system, and newborn screening can find it before symptoms start.
- Each type has a different genetic cause, and the cause matters because some types also have gene therapy or enzyme replacement as options.
- A donor stem cell transplant, from a relative, an unrelated registry volunteer or cord blood, is an established treatment for many forms of SCID.
Find the subtype on your report
The exact diagnosis shapes the treatment options. Your care team can explain the name on your report.
ADA-SCID (adenosine deaminase-deficient SCID)
ADA-deficient SCID is a genetic immune disorder in which a missing enzyme allows toxic metabolites to build up, impairing infection-fighting cells. ADA deficiency can also affect organs outside the immune system and can have later-onset forms.
Cell or gene therapy optionsArtemis-deficient SCID (DCLRE1C)
Artemis-deficient SCID is caused by DCLRE1C variants that impair DNA repair needed to build immune-cell receptors. Severe forms lack effective T- and B-cell immunity; partial defects can present differently or later.
Donor transplant optionX-linked severe combined immunodeficiency (X-SCID)
IL2RG-associated SCID disrupts immune signaling needed for T-cell and natural-killer-cell development. B cells may be present but function poorly. Some IL2RG variants cause less typical, later presentations.
Donor transplant optionIL7R-deficient SCID
IL7R-deficient SCID is a genetic disorder that prevents normal T-cell development. B cells and natural-killer cells are typically present, but the lack of effective T-cell immunity leaves a child vulnerable to serious infection.
Donor transplant optionJAK3-deficient SCID
JAK3-deficient SCID is a recessive genetic disorder that disrupts immune signaling. T cells and natural-killer cells are usually profoundly reduced, while B cells may be present but cannot provide normal protection.
Donor transplant optionRAG1 deficiency
RAG1 deficiency impairs the DNA rearrangement needed to build T- and B-cell receptors. Severe loss of function can cause SCID; partial function can cause Omenn syndrome or later combined immunodeficiency with infection and immune dysregulation.
Donor transplant optionRAG2 deficiency
RAG2 deficiency impairs the DNA rearrangement needed to build T- and B-cell receptors. Severe loss of function can cause SCID; partial function can cause Omenn syndrome or later combined immunodeficiency with infection and immune dysregulation.
Donor transplant option
Common questions
Is SCID the same as “bubble boy disease”?
Yes. “Bubble boy disease” is a nickname for SCID, which became widely known in the 1970s and 1980s. SCID is really a group of rare inherited conditions in which a child is born with very little or no immune system, so a baby cannot fight off infections the way other babies can.
What are the first signs of SCID?
Signs usually show up within the first year of life and generally include repeated infections. In X-linked SCID, the most common form, untreated babies can also have poor growth, ongoing diarrhea, a fungal infection called thrush and skin rashes. Newborn screening can find many babies before any symptoms start. That matters, because the sooner treatment begins, the lower the chance of a dangerous infection.
How is SCID diagnosed?
In the US, every state includes SCID in newborn screening, so a baby may be flagged before any symptoms appear. A flagged result needs urgent follow-up with specialists. They use blood tests that count different kinds of immune cells (T, B and NK cells). If T cells are very low, genetic testing looks for the exact cause, which matters because it shapes the treatment options.
Is SCID curable?
It can be. For many forms of SCID, a donor stem cell (bone marrow) transplant is an established treatment. It gives the child healthy infection-fighting cells and can cure the condition, though not every child is cured. Some types also have gene therapy or enzyme replacement options. Babies diagnosed in infancy and treated in the first three months of life have the highest success rates.
Can a brother or sister be the bone marrow donor for a child with SCID?
Sometimes. A brother or sister whose tissue type matches offers the greatest chance of a cure, but a matched sibling is often not available. Children’s Hospital of Philadelphia says most of its patients instead receive cells from a parent or an unrelated matched volunteer donor. In a study of 902 children with SCID transplanted at 34 US and Canadian centers, five-year survival rose from 72–73% (1982–2009) to 87% (2010–2018), and was highest in babies found through newborn screening.
Is SCID inherited?
Yes. SCID is a group of genetic conditions, and the pattern depends on which gene is involved. X-linked SCID, the most common form, typically affects boys. Other forms, such as those caused by RAG1 or RAG2 changes, need changes in both copies of a gene and affect boys and girls equally. A genetic counselor can explain what this could mean for future children.
Support for patients and families
These independent organizations offer information and support. JBF is not affiliated with them.
- SCID Foundation Shares SCID information, hosts an online family community, and offers Path Forward Scholarships to U.S. families during SCID treatment.United States
- Immune Deficiency Foundation Explains SCID and its types, and works to improve diagnosis, treatment and quality of life for people with primary immunodeficiency.United States
- International Patient Organisation for Primary Immunodeficiencies (IPOPI) International association of national patient groups for primary immunodeficiency, working to improve patients' lives and earlier diagnosis worldwide.Worldwide
Someone may be waiting for a match.
Some people with severe combined immunodeficiency (SCID) are treated with a transplant from a donor. When no relative matches, that donor is often a stranger who joined a registry.
Join the registry
JBF points you to the official registry that serves your country. It explains who can join and what donation involves.
Help a family run a drive
If someone you love needs a donor, a registration drive can add many potential donors at once, for them and for others.
Support this work
Gifts to the Jada Bascom Foundation support donor-awareness education like this guide, community outreach, drive planning and referrals to official registries.
Sources and further reading
- Inborn Errors of Immunity
EBMT Handbook / NCBI Bookshelf, 2024; accessed September 5, 2026 - Adenosine Deaminase Deficiency
GeneReviews / NCBI Bookshelf, Accessed September 5, 2026 - X-Linked Severe Combined Immunodeficiency
GeneReviews / NCBI Bookshelf, Accessed September 5, 2026 - Severe Combined Immunodeficiency (SCID)
Children's Hospital of Philadelphia, Page undated; accessed 2026-09-24 - X-linked severe combined immunodeficiency
MedlinePlus Genetics (NIH National Library of Medicine), Last updated March 18, 2022; accessed 2026-09-24 - Measuring the effect of newborn screening on survival after haematopoietic cell transplantation for severe combined immunodeficiency: a 36-year longitudinal study
The Lancet (Thakar MS et al., Primary Immune Deficiency Treatment Consortium), July 2023; accessed 2026-09-24 - About Primary Immunodeficiency (PI)
CDC, Last updated April 20, 2026; accessed 2026-09-24
