Primary graft failure after umbilical cord blood transplantation (UCBT) is an uncommon but potentially fatal complication, particularly in pediatric patients with relapsed acute lymphoblastic leukemia (ALL). Optimal salvage strategies after graft failure—including choice of conditioning regimen and donor selection for a second transplant—have not been clearly established. This case report describes a child with relapsed precursor B-cell ALL who experienced primary graft failure after an initial UCBT and subsequently underwent a successful second UCBT as salvage.
The patient was a 9-year-old boy with relapsed B-cell precursor ALL who had achieved a second complete remission prior to transplantation. Further demographic or baseline laboratory details beyond age, sex, diagnosis, and remission status were not reported in the abstract of the source.
The first transplantation used a single cord blood unit that, according to the report, had a relatively low dose of CD34-positive cells and considerable mismatches in human leukocyte antigen (HLA) and ABO type. The transplant followed a myeloablative conditioning regimen. Despite this, neutrophil engraftment did not occur and donor chimerism remained minimal, consistent with primary graft failure. The report identifies the low stem cell dose and significant HLA/ABO incompatibility as notable factors in the initial graft outcome.
Given the primary graft failure and absence of a more suitable donor, the clinical team proceeded to an urgent second UCBT. Selection criteria for the second cord blood unit emphasized improved HLA compatibility and substantially higher cell content: notably increased total nucleated cell count and a markedly higher CD34-positive cell dose compared with the first unit. The decision prioritized donor–graft characteristics believed to influence engraftment likelihood when a matched related or unrelated donor was not available.
For the second UCBT the team used a reduced-intensity conditioning approach consisting of fludarabine combined with low-dose total body irradiation (TBI). Specific dosing details, timing, and additional agents (if any) were not provided in the abstract. The choice of reduced-intensity conditioning in this urgent salvage context was reported as the regimen used prior to infusion of the second cord blood unit.
Following the second UCBT, the patient achieved sustained neutrophil engraftment on day +34 post-transplant. After engraftment, the patient maintained stable full donor chimerism. These outcomes indicate successful hematopoietic recovery after the second graft infusion in this pediatric case.
The case report documents several post-transplant complications that occurred after the second UCBT: hemophagocytic syndrome, sinusoidal obstruction syndrome, acute graft-versus-host disease (GVHD), and viral reactivation. According to the report, each of these complications was recognized and managed successfully, though the abstract does not provide granular detail on diagnostic criteria, severity grading, specific therapeutic interventions, or timelines for complication onset and resolution.
This pediatric case illustrates that a second UCBT can be a feasible and effective salvage option after primary graft failure when rapid intervention is possible and no alternative donor is available. The report highlights two modifiable donor/graft factors associated with the initial graft failure—low CD34-positive cell dose and substantial HLA mismatch—and contrasts these with the improved cell doses and compatibility used for the second transplant. It also demonstrates that a reduced-intensity conditioning regimen (fludarabine plus low-dose TBI) can be employed in the salvage setting and still permit eventual sustained engraftment.
Clinicians should note that post-transplant infectious, inflammatory, and hepatic complications can still occur after successful engraftment; proactive monitoring and prompt management were emphasized in the case but specific protocols were not detailed in the abstract.
In the absence of a better donor option and with prompt decision-making, a second UCBT using a cord blood unit with improved HLA compatibility and higher CD34-positive cell dose, following reduced-intensity conditioning with fludarabine and low-dose TBI, resulted in sustained neutrophil engraftment and stable full donor chimerism in this 9-year-old boy with relapsed B-ALL. The case supports second UCBT as a salvage strategy after primary graft failure, while recognizing that post-transplant complications require careful management. The abstract did not provide further procedural details, long-term follow-up data, or specific management regimens for the reported complications.