Salvage HLA-haploidentical Peripheral Blood Stem Cell Transplantation Using Post-transplant Cyclophosphamide for Recurrent Hemophagocytic Lymphohistiocytosis-associated Graft Failure after Cord Blood Transplantations

We describe a case of immunological rejection occurring twice after cord blood transplantation (CBT) for mixed phenotype blast phase chronic myeloid leukemia that was successfully salvaged by haploidentical peripheral blood stem cell transplantation (haplo-PBSCT) with post-transplant cyclophosphamide (PT-Cy). Pre-engraftment immune reaction (PIR) and subsequent hemophagocytic lymphohistiocytosis (HLH), likely due to HLA mismatch in the graft-versus-host (GVH) direction, lead to poor graft function (PGF) and graft failure (GF). This case highlights the pathophysiology of PIR, HLH, PGF, and GF, collectively termed "post-transplant cytokine syndrome." PT-Cy haplo-PBSCT, with wide donor availability and reduced infection risk leading to HLH via rapid engraftment, may be a suitable salvage option for post-CBT cytokine syndrome-related GF.