Research Studies

1. Patient must be greater than or equal to 1.0 year of age and less than 50.0 years of age at the time of enrollment (i.e. patient must have celebrated their 1st birthday when enrolled and must NOT have celebrated their 50th birthday when enrolled; 49.99 years). 2. Underlying bone marrow failure disorders treatable by allogenic HCT. 3. Patient and/or legal guardian must sign informed consent prior to initiation of conditioning for BMT CTN 1904. 4. Females and males of childbearing potential must agree to practice 2 effective methods of contraception at the same time or agree to abstinence.

1. Patient must be greater than or equal to 1.0 year of age and less than 50.0 years of age at the time of enrollment (i.e. patient must have celebrated their 1st birthday when enrolled and must NOT have celebrated their 50th birthday when enrolled; 49.99 years). 2. Underlying bone marrow failure disorders treatable by allogenic HCT. a. Shwachman-Diamond syndrome b. Diamond Blackfan anemia c. Congenital Sideroblastic anemia d. GATA2 mutation with associated marrow failure e. SAMD9 or SAMD9L disorders f. Congenital amegakaryocytic thrombocytopenia g. Paroxysmal nocturnal hemoglobinuria (PNH) h. An undefined BMFD: a patient with a BMFD for whom a genetic mutation responsible for their bone marrow failure phenotype has not been identified (excluding PNH) will be eligible for this clinical trial following approval by BMT CTN 1904 ERC. i. A BMFD with a known genetic mutation but not listed above will be eligible for this clinical trial following approval by BMT CTN 1904 ERC. 3. Patient and/or legal guardian must sign informed consent prior to initiation of conditioning for BMT CTN 1904. 4. Females and males of childbearing potential must agree to practice 2 effective methods of contraception at the same time or agree to abstinence. Patient Exclusions: 1. Patients with idiopathic aplastic anemia, Fanconi anemia, dyskeratosis congenita, and congenital neutropenia. 2. Patients with MDS as defined by the World Health Organization (WHO) or leukemia. 3. Prior allogeneic transplant 4. Patient's weight less than or equal to10.0 kg (actual body weight and adjusted body weight) at time of study enrollment 5. Lansky (patients < 16 years of age) or Karnofsky (patients greater than or equal to16 years of age) performance <70% 6. Organ Dysfunction defined as follows: a. Cardiac: i. Left ventricular ejection fraction <50% by echocardiogram or multi-gated acquisition (MUGA) scan. ii. For patients unable to obtain a left ventricular ejection fraction, left ventricular shortening fraction <26%. b. Pulmonary: i. DLCO (corrected/adjusted for hemoglobin), FEV1, and FVC <50% predicted. ii. For patients unable to perform pulmonary function tests (PFTs) due to age or developmental delay: Oxygen saturation <92% on room air. iii. On supplemental oxygen. c. Renal: i. Estimated creatinine clearance <60 mL/minute/1.73m2 (estimated per institutional practice). ii. Dialysis dependent d. Hepatic: i. Conjugated bilirubin > 2x upper limit of normal for age (ULN, unless attributable to Gilbert’s syndrome), or ii. AST or ALT > 4x ULN for age, or iii. Fulminant liver failure or cirrhosis 7. Iron overload - This exclusion criterion only applies to patients who are considered at risk for hepatic or cardiac iron overload. 8. Uncontrolled bacterial infection within 1 week of study enrollment. 9. Uncontrolled viral or fungal infection within 30 days of study enrollment. 10. Positive for HIV. 11. Presence of clinically significant anti-donor HLA-antibodies per institutional practice. 12. Prior solid organ transplant. 13. Patients with prior malignancies except resected non-melanoma skin cancer or treated cervical carcinoma in situ. 14. Demonstrated lack of compliance with prior medical care as determined by referring physician. 15. Females who are pregnant or breast-feeding. 16. Known hypersensitivity to treosulfan or fludarabine. 17. Known life-threatening reaction (i.e. anaphylaxis) to Thymoglobulin that would prohibit use for the patient as this study requires use of the Thymoglobulin preparation of anti-thymocyte globulin (ATG).