Diagnosing recipient- vs. donor-derived posttransplant myelodysplastic neoplasm via targeted single-cell mutational profiling.

Background: Distinguishing donor- vs. recipient-derived myelodysplastic neoplasm (MDS) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is challenging and has direct therapeutical implications.

Methods: Here, we took a translational approach that we used in addition to conventional diagnostic techniques to resolve the origin of MDS in a 38-year-old patient with acquired aplastic anemia and evolving MDS after first allo-HSCT. Specifically, we used single-cell transcriptional profiling to differentiate between donor- and recipient-derived bone marrow cells and established a strategy that additionally allows identification of cells carrying the MDS-associated U2AF1^S34Y variant.

Results: The patient exhibited mixed donor chimerism combined with severely reduced erythropoiesis and dysplastic morphology within the granulocytic and megakaryocytic lineage along with the MDS-associated U2AF1^S34Y mutation in the bone marrow. Single-cell transcriptional profiling together with targeted enrichment of the U2AF1^S34Y-specific locus further revealed that, while the immune compartment was mainly populated by donor-derived cells, myelopoiesis was predominantly driven by the recipient. Additionally, concordant with recipient-derived MDS, we found that U2AF1^S34Y-mutated cells were exclusively recipient derived with X but not Y chromosome-specific gene expression.

Conclusion: Our study highlights the clinical potential of integrating high-resolution single-cell techniques to resolve complex cases for personalized treatment decisions.

Funding: The study was funded by intramural resources of the Charité - Universitätsmedizin Berlin and the Berlin Institute of Health.