Background: Malignant infantile osteopetrosis (MIOP) is a rare hereditary disorder of osteoclast function, which can be reversed by hematopoietic stem cell transplantation (SCT). In recent studies defibrotide (DF) demonstrated superior efficacy in the treatment of hepatic veno-occlusive disease (VOD).

Methods: Twenty children with MIOP were consecutively transplanted in our centre between 1996 and 2005. Eleven of these patients were transplanted between 1996 and 2001 without any VOD prophylaxis. Thereafter nine patients were transplanted between 2001 and 2005 with prophylactic DF from the first day of conditioning until 30 days after SCT because we observed a high incidence of VOD in transplanted patients and explored the prevention of this complication by using DF as a prophylaxis.

Results: Patients without DF experienced an overall incidence of VOD of 63.6% (7/11). VOD was severe in three patients and one patient succumbed to VOD related multiorgan failure (MOF). In nine patients consecutively transplanted between 2001 and 2005 only one patient (11.1%) was diagnosed with moderate VOD.

Conclusion: SCT in patients with MIOP is associated with a very high risk to develop VOD. Prophylactic DF was implemented in our current transplant protocol and reduced the VOD rate dramatically in this high risk population.

Disclosures: Defibrotide is not licensed for the treatment of VOD in the US, but it was applied for the orphan drug status which is pending.; Gentium, the company that produces Defibrotide is the Co.-Sponsor of an ongoing prospective clinical trial on VOD in pediatric SCT.

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