Dyskeratosis congenita (DC) is an inherited multisystem disorder, which classically presents with a clinical triad of skin pigment abnormalities, nail dystrophy, and oral leukoplakia. DC is part of a spectrum of telomere biology disorders, which include some forms of inherited idiopathic aplastic anemia, myelodysplastic syndrome, and pulmonary fibrosis and the congenital diseases Hoyeraal-Hreidarsson syndrome and Revesz syndrome. Progressive bone marrow failure (BMF) occurs in more than 80% of patients under 30 years of age and is the primary cause of morbidity and mortality, followed by pulmonary failure and malignancies. Allogeneic hematopoietic cell transplantation (HCT) is curative for the hematological defects, but several studies have demonstrated poor outcomes in DC patients due to increased early and late complications. A predisposition to pulmonary failure, vascular disease and secondary malignancies may contribute to the high incidence of fatal complications following HCT in DC patients, and provides an impetus to reduce exposure to chemotherapy and radiotherapy in preparative regimens. Recent studies suggest that fludarabine-based conditioning regimens provide stable engraftment and may avoid the toxicities seen after HCT for DC, but studies to date are limited to case reports, retrospective studies and a single prospective trial. In this study, we propose to prospectively evaluate the efficacy of a fludarabine- and antibody-based conditioning regimen in HCT for DC patients, with the goals of maintaining donor hematopoiesis and transfusion independence while decreasing early and late complications of HCT for DC.