Inherited immune disorders
Adenosine deaminase-deficient severe combined immunodeficiency
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.
Other names and abbreviations
ADA-SCID · ADA deficiency · ADA-deficient SCID · SCID · bubble boy disease · Severe combined immunodeficiency due to ADA deficiency · Adenosine deaminase deficiency with SCID
Where transplant fits
Allogeneic transplantation and autologous stem-cell gene therapy can restore immune function. Gene therapy uses the patient’s own cells. A suitable related or unrelated donor may be used for transplantation, depending on clinical circumstances and available treatments.
Treatment depends on the exact diagnosis, disease stage, prior treatment and the person’s health. These categories are not estimates of donor demand.
Treatment at a glance
- Who it affects
- Classic ADA-SCID usually presents early in life, but partial defects can cause delayed combined immunodeficiency.
- Other treatment options
- ADA enzyme replacement can rapidly reduce metabolic toxicity and is often used while definitive treatment is arranged. Gene-therapy access is geographically restricted; Strimvelis has an EU indication when a suitable matched related donor is unavailable.
- Cells used for transplantation
- Donor blood-forming stem cells for allogeneic transplantation, or the patient’s own gene-modified stem cells for autologous gene therapy.
Why the details matter
Restoring immune function does not guarantee reversal of existing neurologic or other organ injury. Later-onset ADA deficiency must not automatically inherit the same transplant pathway as classic SCID.
Questions to bring to your care team
What is the exact diagnosis or subtype? What is the goal of each treatment option? If transplant is being considered, why does it fit this situation, which cells would be used and what are the alternatives?
Sources and further reading
- Adenosine Deaminase Deficiency
GeneReviews, University of Washington / NCBI Bookshelf · Accessed 2026-09-05 - Strimvelis
European Medicines Agency · Accessed 2026-09-05 - Guidelines for hematopoietic stem cell transplantation for inborn errors of immunity
EBMT / ESID Inborn Errors Working Party · 2021
Understanding can become action.
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