Inherited immune disorders
Adenosine deaminase-deficient severe combined immunodeficiency
Also called: ADA-SCID · ADA deficiency · ADA-deficient SCID · SCID · bubble boy disease · Severe combined immunodeficiency due to ADA deficiency · Adenosine deaminase deficiency with SCID
What a donor has to do with this
An approved gene or cell therapy now exists for this condition and can be an alternative to a donor transplant. Which route fits a person depends on their situation, and that decision belongs to them and their treating team.
This is our reading of published transplant guidelines for this condition, not a measurement of how many people need a donor. Where a source actually counted donors, the figure and the people it counted are shown further down. Where none did, we say so rather than estimate.
This page is not written out in full yet
We have not written this condition out in full yet. What is on this page — how a donor fits in, who it affects, and the sources behind that — is researched and linked, but the plain-English explanation of the condition itself is still to come.
What the evidence says
- Who it affects
- Typical onset/diagnosis: classic ADA-SCID usually presents in the first 6 months, while 15–20% present at ages 1–10 years or later. Evidence: U.S. NIH GARD synthesis (updated 2026); no markedly enriched population was identified.
- Treatments other than a transplant
- Strimvelis (autologous CD34+ gene therapy) — approved — European Union, 2016 — For ADA-SCID without a suitable HLA-matched related donor; availability is geographically restricted.; PEGylated ADA enzyme replacement — approved/supportive bridge — multiple regions — Restores detoxification but is generally a bridge or fallback rather than definitive immune reconstitution.
- If a transplant is used, the cells come from
- bone marrow: used in opened IEI transplant guidance; disease-specific share was not reported; mobilized peripheral blood stem cells: used in opened IEI transplant guidance; disease-specific share was not reported; umbilical cord blood: used as an alternative in opened IEI transplant guidance; disease-specific share was not reported; dominance: no dominant graft source was reported in the opened disease-specific sources
- How often the donor was unrelated
- Not reported. No source we could read states this for this condition, so we do not give a number. An estimate here would be a guess dressed as evidence.
Where this gets complicated
ADA deficiency can also present as delayed-onset combined immunodeficiency or partial enzyme deficiency; those phenotypes should not automatically be counted as transplant candidates.; The 2021 guideline predates several later access and commercialization changes, so Strimvelis availability must be checked locally.
“In ADA-deficiency three therapeutic options are available including Enzyme replacement Therapy (ERT) and gammaretroviral gene therapy”
It describes what teams consider in general. It cannot say what applies to any one person. Read the source.
Registries need people
An unrelated donor is not a usual part of treating this condition. Registering still matters, for the many conditions where it is.
Joining a registry is a cheek swab and a short health form. You are not matched to a condition — you are matched to a person, and it could be someone with any of the conditions in this library. You are contacted only if you turn out to be a possible match for someone, and you can ask questions and decline before anything else happens.
Related conditions
Others in inherited immune disorders. They are genuinely different diseases with different treatments — the group name is not a diagnosis.
Where this came from
- Severe combined immunodeficiency due to adenosine deaminase deficiency — NIH NCATS GARD, updated 2026-06
- Guidelines for hematopoietic stem cell transplantation for inborn errors of immunity — EBMT/ESID Inborn Errors Working Party, 2021
- EBMT Handbook, Chapter 90: Inborn Errors of Immunity — EBMT/Springer, 2024-04-11