Challenges in HLA and ABO typing of deceased organ donors with prior hematopoietic stem cell transplantation: two cases and practical considerations for evaluation.

BACKGROUND

Prior allogeneic hematopoietic stem cell transplantation (HSCT) can complicate HLA and ABO typing of deceased organ donors because circulating hematopoietic cells and organs may originate from different sources.

CASE PRESENTATIONS: We describe two deceased organ donors with prior HSCT. In Case 1, historical records demonstrated discordance at HLA-C and HLA-DQ between the HSCT donor and the constitutional pre-HSCT typing. Peripheral-blood HLA typing reflected the HSCT donor, while a kidney blood-vessel specimen yielded four DPB1 alleles from mixed sources, permitting only a presumptive kidney DPB1 assignment. In Case 2, HLA assignments were concordant after childhood HSCT, but ABO serology was O/A ambiguous, resulting in allocation as blood group AB. Retrospective molecular ABO genotyping and chimerism testing demonstrated mixed donor- and recipient-derived DNA in buccal specimens.

CONCLUSIONS

HSCT-associated chimerism can complicate deceased-donor HLA and ABO typing. Interpretation should integrate transplant history, historical records, specimen source, serology, and molecular testing when indicated.