LAUSR

Introduction high dose methotrexate (HD-MTX) regimen is used in osteosarcoma, leukemia and lymphoma treatment. Osteosarcoma is mostly diagnosed in children and adolescents. Most frequent methotrexate toxicities are mucositis, myelosuppression, renal failure, hepatitis and necrotizing encephalopathy. Toxicities increase with renal impairment, denutrition, in older patients, with some pharmacogenetics factors or with drug interactions. Case report We report a 16th years old woman diagnosed with osteosarcoma and experienced an unexpected severe hepatic and skin toxicities as toxic epidermal necrolys, Steven Johnson syndrome. Management and outcome This toxicity occurred despite acid folinic rescue performed as good practice recommendation. Fourteen hours after methotrexate administration, renal failure was observed and after 72 h an erythematous rash and epidermal detachment with toxic epidermal necrolys. Seven days after methotrexate administration, hepatic failure began until grade IV cytolysis. High dose of folinic acid were administered during all severe toxicities. Methotrexate were not longer administered to this young patient and chemotherapy with ifosfamide (IFO), doxorubicine and cisplatin were performed in this patient and complete histologic response were observed in the surgical bone resection. Discussion No classical toxicities risk factors were identified in this patient but a homozygote mutation of MTHFR gene and homozygote SLCO1B1 gene mutation were found. MTHFR and SLCO1B1 are both implicated in methotrexate metabolism.