INTRODUCTION
Diamond-Blackfan anemia (DBA) is a rare inherited bone marrow failure syndrome (IBMFS) characterized by hypoproliferative and proapoptotic erythropoiesis along with malformations and cancer predisposition.1 The pure red cell aplasia (PRCA) arises from haploinsufficiency due to a loss of function mutation in ribosomal protein (RP)-encoding genes. Corticosteroids are the first-line treatment for PRCA in infancy, but >20% of patients result in transfusion-dependency. Patients are predisposed to myeloid malignancy and solid tumors. In pediatric patients, the 5-year chronic graft-versus-host-disease (GVHD)-free survival rate following allogeneic hematopoietic cell transplantation (HCT) has improved to 87.0%, including mostly histocompatible sibling or unrelated donors.2 HCT can achieve a hematological cure transfusion-dependent young patients if a suitable donor is available. Nevertheless, conditioning of alternate donor HCT is carefully personalized according to organ dysfunctions associated with the ribosomopathy by itself and iron-overload. Regarding cancer predisposition and the high risk of complications, reduced intensity conditioning (RIC) is preferable; however, there is limited information on unrelated donor HCT.3-7 To optimize the HCT regimen for DBA, we assessed the outcomes of recent cases with alternate donor bone marrow transplantation (BMT) following targeted busulfan (BU)-based intermediate intensity conditioning.