Reduced methotrexate clearance and renal impairment in a boy with osteosarcoma and earlier undetected autosomal dominant polycystic kidney disease (ADPKD).

We report a 12-year-old boy with osteoblastic osteosarcoma of the right femur. He was started on chemotherapy according to the EURAMOS/COSS 1 protocol. Chemotherapy with doxorubicin/cisplatin resulted in reversible acute renal failure and methotrexate levels were repeatedly elevated. Family history suggested an autosomal dominant polycystic kidney disease. Genetic testing revealed a novel mutation c.10707_10712del (p.Val3569_3570del) in exon 36 of the PKD1 gene. Patients with autosomal dominant polycystic kidney disease may be at risk for acute renal failure during chemotherapy without signs of renal impairment. A careful family history is important to exclude risk factors for renal impairment before introducing high-dose chemotherapy.