Myeloablative Conditioning, Prophylactic Defibrotide and Haplo AlloSCT for Patients With Sickle Cell Disease

Inclusion Criteria: * Disease: Homozygous Hemoglobin S Disease, or Hemoglobin S B0/+ thalassemia, or Hemoglobin SC Disease, or Beta thalassemia intermedia/majora * Patients must demonstrate one or more of the following Sickle Cell Disease Complications (or patients in Cohort 2 can meet other high risk criteria instead) * Clinically significant neurologic event (stroke) or any neurologic deficit lasting \>24 hours that is accompanied by an infarct on cerebral MRI * Acute chest syndrome in the preceding two year period prior to enrollment that have failed, been non-compliant or declined hydroxyurea treatment, or prior to chronic RBC transfusion therapy, exchange transfusion or erythrocyte pheresis. * Recurrent painful events (at least 3 in the 2 years prior to enrollment or prior to chronic chronic RBC transfusion therapy, exchange transfusion or erythrocyte pheresis). * Abnormal TCD study requiring starting on chronic transfusion therapy and/or exchange transfusions. * At least one silent infarct lesion on a MRI scan of the head. Or (directly or probably related to SCD) * Sickle Cell nephropathy; * Splenic sequestration requiring RBC transfusion; * Aplastic crisis requiring RBC transfusion; * Avascular necrosis of the hip diagnosed by MRI; * Two episodes or more of leg ulcerations; * Recurrent priapism . * Infant dactylitis. * OR for Cohort #2 ONLY: Patient must be between 18 and 34.99 years of age, patients must demonstrate at least two of the following: * WBC \> 13,500 cells/microliter at baseline when not acutely ill (on two separate occasions) \> 2 weeks from a VOC event or hospitalization. * Tricuspid Regurgitant Jet Velocity (TRV) \> 3.0 m/s * Requiring Chronic Monthly Transfusions ( \> 12 transfusions in the 12 months) * History of sepsis * N-terminal pro-brain natriuretic peptide (NT-proBNP) \> 160 ng/L at clinical baseline when not acutely ill or hospitalized. * all patients must meet disease, age, organ function and donor criteria; Exclusion Criteria: * Patients who are receiving concomitant systemic anticoagulants and/or fibrinolytic therapies. * Patients with a previously known hypersensitivity reaction to defibrotide. * Females who are pregnant or breast-feeding are not eligible * SCD Patients with documented uncontrolled infection at the time of study entry are not eligible. * SCD patients who have an unaffected HLA matched family donor willing to proceed to donation will not be eligible for this study. * Karnofsky or Lansky (age appropriate) Performance Score \<50% (hemiplegia alone secondary to a previous stroke is not an exclusion) * Demonstrated lack of compliance with medical care. * Patients with clinically significant fibrosis or cirrhosis of the liver will not be eligible. * Patients who have previously received a HSCT will not be eligible. * Patients with contraindications to the use of defibrotide