This study evaluates the safety of defibrotide in subjects with sickle cell disease (SCD)-associated acute chest syndrome (ACS).

Inclusion Criteria:

• SCD-associated ACS with the presence of any two or more of the following signs not explained by other etiologies: Fever, Chest pain, Cough, Dyspnea, Tachypnea for age, Pulmonary infiltrate on CXR and/or Chest CT scan, Decreased O2 saturation with or without oxygen supplement;
• Age 2 to 40 years of age;
• Homozygous Hemoglobin S Disease, Hemoglobin SC Disease or Hemoglobin S 0/+ thalassemia;
• Informed consent/assent;
• Consent of patient/parent within ≤72 hours after inpatient admission for SCD-associated ACS.
• Females of childbearing age will have a negative pregnancy test.

Exclusion Criteria:

• Current Grade III or IV hemorrhage;
• Previous hypersensitivity reaction to defibrotide;
• Current systemic anti-coagulant therapy and/or fibrinolytic therapy;
• Consent of patient/parent greater than 72 hours of inpatient admission for SCD-associated ACS;
• No signed informed consent