1 Paediatric Bone Marrow Transplant, Royal Manchester Children's Hospital, Manchester NHS Foundation Trust, Manchester, UK.
2 Department of Haematology, Erasmus Medical Center Cancer Institute, University Medical Center Rotterdam, Rotterdam, Netherlands.
3 Department of Hematology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.
4 Department of Stem Cell Transplantation, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. Electronic address: nico.gagelmann@posteo.de.