Inherited immune disorders
IL2RG-associated X-linked severe combined immunodeficiency
Also called: X-SCID · SCID-X1 · IL2RG deficiency · gamma-c deficiency · SCID · severe combined immunodeficiency · bubble boy disease · X-linked severe combined immunodeficiency
What a donor has to do with this
For some people with this condition, a transplant using blood stem cells from an unrelated donor is part of the treatment guidelines. When a transplant is the right route and no one in the family matches, that donor comes from a registry. Not everyone with this condition has a transplant, and many never need one.
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.
What the evidence says
- Who it affects
- Typical onset/diagnosis: affected boys usually present in infancy, and SCID commonly becomes clinically apparent in the first 3–6 months without newborn screening. Evidence: international EBMT synthesis (2024); geographic and ethnic variation is noted, but no IL2RG-specific enriched population was identified.
- Treatments other than a transplant
- Investigational autologous gene therapy — not approved — clinical trials — Not coded as an approved direct substitute.
- 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
Unconditioned matched-family grafts may restore T cells yet leave inadequate B-cell or myeloid chimerism; conditioning decisions are genotype- and donor-dependent.; Gene therapy is clinically active but was not an approved product at the evidence cutoff.
People with this condition need donors
Joining a registry is a cheek swab and a short health form. 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 disease — NIH NCATS GARD, updated 2026-06
- EBMT Handbook Table 90.2: Main characteristics of severe combined immunodeficiencies — EBMT/Springer, 2024-04-11
- Guidelines for hematopoietic stem cell transplantation for inborn errors of immunity — EBMT/ESID Inborn Errors Working Party, 2021