Jada Bascom Foundation
All conditions

Histiocytic disorders

Familial hemophagocytic lymphohistiocytosis

Also called: FHL · FHLH · primary HLH · familial HLH · HLH · hemophagocytic lymphohistiocytosis · Primary familial hemophagocytic lymphohistiocytosis · Familial erythrophagocytic lymphohistiocytosis

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.

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: disease is usually apparent during infancy, although later childhood or adolescent presentation occurs. Evidence: U.S. NIH GARD synthesis (updated 2026); no markedly enriched population was identified.
Treatments other than a transplant
HLH-directed immune-chemotherapy or cytokine blockade — bridge to curative HCT — multiple regions — Disease control before transplant is essential; these therapies are not definitive for germline FHL.
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

This row excludes secondary HLH and macrophage activation syndrome, which are not inherited transplant indications by default.; Reduced-intensity conditioning can reduce toxicity but mixed chimerism may permit relapse; acceptable donor chimerism thresholds vary.

Registries need people

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.

Find your registry

Related conditions

Others in histiocytic disorders. They are genuinely different diseases with different treatments — the group name is not a diagnosis.

Where this came from