Introduction: Fanconi anemia (FA) is a rare, genetic disorder clinically characterized by congenital abnormalities, progressive bone marrow failure (BMF), and a predisposition to malignancies. Allogeneic hematopoietic stem cell transplantation (HSCT) is currently the only curative treatment for BMF. In patients with FA who do not have a matched sibling donor, HSCT conditioning regimens typically use reduced doses of cyclophosphamide, fludarabine and anti-thymocyte globulin (ATG) with total body irradiation (TBI) or busulfan. However, treatment is complicated by conditioning related toxicities, graft vs host disease (GvHD) and increased predisposition to malignancies later in life. Prior attempts to remove TBI from FA conditioning regimens have been unsuccessful due to increased risk of graft rejection - and alternative approaches have replaced TBI with busulfan which is still genotoxic.