¹Department of Bone Marrow Transplantation, Great Ormond Street Hospital for Children NHS Trust, London, UK

Correspondence: Dr P Veys, Department of Bone Marrow Transplantation, Great Ormond Street Hospital for Children NHS Trust, Great Ormond Street, London WC1N 3JH, UK. E-mail: veysp@gosh.nhs.uk

Abstract

Allogeneic stem cell transplant is curative for haemophagocytic lymphohistiocytosis (HLH) and refractory Langerhans cell histiocytosis (LCH). However, patients frequently have significant pre-transplant morbidity and there is high TRM. Because HLH is caused by immune dysregulation, we surmised that a reduced-intensity conditioned (RIC) regimen might be sufficient for cure, while decreasing the TRM. In 2006, we reported the outcome of 12 patients treated with RIC SCT from a matched family/unrelated or haploidentical donor. Here we discuss the update of these patients, including a total of 25 patients treated with RIC SCT for HLH and three for LCH. Twenty-one of the twenty-five patients with HLH (84%) are alive and well with remission at a median of 36 months from SCT. Mortality included pneumonitis (n=3) and hepatic rupture (n=1). All three patients treated with RIC SCT for LCH remain alive and in remission at a median of 5.1 years from SCT. Seven of twenty-four survivors (one with LCH) have mixed chimerism but remain disease-free. These data are supported by other groups including 100% survival in seven patients with HLH and 78% survival of nine patients with LCH. In summary, RIC compares favourably with conventional SCT with long-term disease control in surviving patients with both HLH and LCL, despite a significant incidence of mixed chimerism.