Thrombotic microangiopathy (TMA) is a common complication in the stem cell transplant
population. Certain populations within the hematopoietic stem cell transplant (HSCT)
population are at a higher risk than others. Defibrotide is an endothelial stabilizing agent
which may prevent the endothelial damage that triggers TMA in HSCT patients. The feasibility,
safety, and efficacy of defibrotide prophylaxis in a pediatric transplant population is
unknown. Twenty five patients age 0 to 30 years receiving autologous or allogeneic
hematopoeitic stem cell transplant who meet TMA high risk criteria will be enrolled. Patients
will receive Defibrotide for 28-35 days starting before conditioning, and will be closely
monitored for any adverse events up through 6 months post-transplant. The feasibility of
administering defibrotide will be evaluated as well as incidence of TMA.