Inherited immune disorders
MHC class II deficiency
Also called: BLS II · BLS2 · MHC II deficiency · HLA class II deficiency · Bare lymphocyte syndrome type II · HLA class II-negative severe combined immunodeficiency · MHC class II expression deficiency
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: both sexes usually present with infections in the first year of life. Evidence: international/Indian reviews (2018–2019); over 150 patients had been reported, about two-thirds of North African descent, with incidence reaching 20–30% of SCID in Kuwait and North Africa.
- Treatments other than a transplant
- Antimicrobial prophylaxis and immunoglobulin replacement — supportive/bridge to HCT — multiple regions — Does not restore MHC class II expression.
- If a transplant is used, the cells come from
- bone marrow: conventional and most frequently reported source in the opened review; mobilized peripheral blood stem cells: used increasingly with reduced-toxicity conditioning; umbilical cord blood: used in multiple opened transplant series; dominance: bone marrow was the conventional dominant source in the opened historical series
- 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
TREC-based newborn screening can miss MHC class II deficiency because TRECs may remain measurable.; The 2019 international review summarized more than 100 transplants; modern reported overall survival ranged from 66% to 100%, but no donor-route share was inferred.
“Hematopoietic cell transplantation (HCT) is the only established curative therapy for MHC class II deficiency”
It describes what teams consider in general. It cannot say what applies to any one person. Read the source.
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
- MHC class II 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
- Hematopoietic Cell Transplantation for MHC Class II Deficiency — Frontiers in Pediatrics, 2019-12-11
- Clinical, Immunological, and Molecular Findings in Five Patients with MHC Class II Deficiency from India — Frontiers in Immunology, 2018