Haematopoietic stem-cell transplantation

Overview & Definition

A child relapses with leukaemia, or is born with a faulty haemoglobin, or fails to make any white cells at all, and the question becomes whether to replace the entire blood-forming system. That replacement is the haematopoietic stem-cell transplantation, and it sits at the most intensive end of paediatric medicine. The candidate who can hold the intent of the procedure, donor choice, conditioning and the complications together has the framework that organises a large block of the fellowship syllabus, because the transplant pulls in oncology, immunology, hepatology and infectious disease at the same time. The acuity is high, the course is long, and the complications are the everyday reality of the transplant ward. [1]

Haematopoietic stem-cell transplantation is the infusion of haematopoietic stem cells after conditioning chemotherapy, with or without radiation, to rescue the marrow and, in the allogeneic form, to confer a new immune system with a graft-versus-leukaemia effect. The procedure is split into the autologous transplant, in which the child's own cells are collected and reinfused, and the allogeneic transplant, in which the cells come from a donor. The autologous form is a rescue that allows the high-dose chemotherapy, while the allogeneic form is an immune replacement that carries the graft-versus-leukaemia benefit and the graft-versus-host disease. The single most important distinction the candidate holds is between these two, because every decision that follows, the donor search, conditioning, prophylaxis and the complications, flows from it. [1][5]

The allogeneic transplant dominates this topic because it generates the complications that the exam tests. The donor is the organising variable, and the search moves from the matched sibling donor, the preferred source, through the matched unrelated donor, the haploidentical family donor and the umbilical cord blood unit, each with its own matching requirement, cell dose and risk profile. The graft-versus-leukaemia effect is the immunological prize of the allogeneic transplant, and the graft-versus-host disease is its price, and the modern practice is a constant negotiation between the two. The conditioning, whether myeloablative or reduced-intensity, determines the toxicity, the engraftment speed and the risk of the hepatic sinusoidal obstruction syndrome. [2][3]

The survival after a paediatric transplant depends on the disease, donor, conditioning and the complications, and the contemporary outcomes range from over ninety percent for the matched sibling transplant of a benign disease to under forty percent for the refractory leukaemia with the severe graft-versus-host disease. The candidate who carries these numbers, alongside the recognition of the transplant emergencies, holds the reasoning the boards reward. The rash, the diarrhoea, the jaundice and the fever in the post-transplant child are never dismissed, because each maps to a complication that demands a specific response. [1][12]

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1. [1]Kanate AS, Majhail NS, Savani BN Indications for Hematopoietic Cell Transplantation and Immune Effector Cell Therapy: Guidelines from the American Society for Transplantation and Cellular Therapy Biol Blood Marrow Transplant, 2020.PMID 32165328
2. [2]Mangum DS, Caywood E A clinician's guide to HLA matching in allogeneic hematopoietic stem cell transplant Hum Immunol, 2022.PMID 35346535
3. [3]Alsultan A, Abujoub R, Elbashir E The effect of intensity of conditioning regimen on the outcome of HSCT in children with sickle cell disease Clin Transplant, 2022.PMID 35929611
4. [4]Bolaños-Meade J, Hamadani M, Wu J Post-Transplantation Cyclophosphamide-Based Graft-versus-Host Disease Prophylaxis N Engl J Med, 2023.PMID 37342922
5. [5]Zeiser R, Blazar BR Acute Graft-versus-Host Disease - Biologic Process, Prevention, and Therapy N Engl J Med, 2017.PMID 29171820
6. [6]Jagasia MH, Greinix HT, Arora M National Institutes of Health Consensus Development Project on Criteria for Clinical Trials in Chronic Graft-versus-Host Disease: I. The 2014 Diagnosis and Staging Working Group report Biol Blood Marrow Transplant, 2015.PMID 25529383
7. [7]Zeiser R, Polverelli N, Ram R, et al. Ruxolitinib for Glucocorticoid-Refractory Chronic Graft-versus-Host Disease N Engl J Med, 2021.PMID 34260836
8. [8]Mohty M, Malard F, Alaskar AS Diagnosis and severity criteria for sinusoidal obstruction syndrome/veno-occlusive disease in adult patients: a refined classification from the European Society for Blood and Marrow Transplantation Bone Marrow Transplant, 2023.PMID 37095231
9. [9]Larue M, Malard F, Alaskar AS Management of liver sinusoidal obstruction syndrome/veno-occlusive disease in adults: a 2025 perspective from an international expert group Bone Marrow Transplant, 2025.PMID 40263636
10. [10]Aziz MT, Kakadiya PP, Kush SM Defibrotide: An Oligonucleotide for Sinusoidal Obstruction Syndrome Ann Pharmacother, 2018.PMID 28914546
11. [11]Kharfan-Dabaja MA, Kumar A, Ayala E, et al. Standardizing Definitions of Hematopoietic Recovery, Graft Rejection, Graft Failure, Poor Graft Function, and Donor Chimerism in Allogeneic Hematopoietic Cell Transplantation Transplant Cell Ther, 2021.PMID 34304802
12. [12]Lehrnbecher T, Robinson P, Fisher B Guideline for the Management of Fever and Neutropenia in Children With Cancer and Hematopoietic Stem-Cell Transplantation Recipients: 2017 Update J Clin Oncol, 2017.PMID 28459614