Fludarabine, Campath, and Low-Dose Cyclophosphamide (FCClow) with or without TBI Conditioning Results in Excellent Transplant Outcomes in Children with Severe Aplastic Anemia

•Fludarabine, Campath, and low-dose cyclophosphamide (FCClow) and low-dose total body irradiation (for unrelated donor graft) conditioning for allogeneic hematopoietic stem cell transplant (HSCT) in children with severe aplastic anemia (SAA) results in excellent cure rates.•Use of peripheral blood stem cell source for alemtuzumab-based conditioning in children with SAA does not increase the risk of chronic graft-versus-host disease or severe viral infections.•FCClow ± TBI conditioning regimen is associated with stable mixed T cell and full myeloid donor chimerism post-HSCT. Various reduced-intensity conditioning regimens are in use for allogeneic hematopoietic cell transplant (HSCT) in patients with idiopathic severe aplastic anemia (SAA). We describe the use of fludarabine, Campath, and low-dose cyclophosphamide (FCClow) conditioning in 15 children undergoing related or unrelated donor transplants. Total body irradiation (TBI) of 2 Gy was added for unrelated donor HSCT. At a median follow-up of 2.3 years, the failure-free survival was 100%, with low rates of infection and toxicity. There was no occurrence of grade III to IV acute graft-versus-host disease (GVHD). All patients had full donor myeloid chimerism post-HSCT, even with mixed chimerism in the T cell lineage. The absence of chronic GVHD and long-term stable mixed donor T cell chimerism confirms immune tolerance following FCClow (± TBI) conditioned transplantation in children with SAA.