Treosulfan Therapeutic Drug Monitoring in Pediatric Hematopoietic Stem Cell Transplant Recipients

Inclusion Criteria: * Age range 0 - 18 years. * Life expectancy \> 12 weeks. * Diagnosis of malignant or non-malignant disorder. * Pre-HSCT Lansky / Karnofsky score ≥ 40%. * Indication to allogeneic or autologous HSCT with TREO as part of the pre-transplant conditioning regimen. * Negativity of pregnancy test for female patients. * Written informed consent signed by the parents or guardians. Exclusion Criteria: * Absence of written informed consent signed by the parents or guardians. * Current clinically active infectious disease (including positive HIV serology or viral RNA). * Severe cardiovascular disease (arrhythmias requiring chronic treatment, congestive heart failure or left ventricular ejection fraction \<40%). * Liver dysfunction (AST/ALT ≥ 3 times institutional upper limit normal value -ULN- or bilirubin \> 3 times ULN). * Renal dysfunction: serum creatinine \> 1.5 times ULN or calculated creatinine clearance \< 60 ml/min/1.73 m2 * End stage irreversible multi-system organ failure. * Pregnant or breast feeding female patient.