Thrombosis, defined as venous and/or arterial thromboembolism, has a higher incidence in paediatric oncology patients and is reported with both E. coli- and Erwinia-derived asparaginase (mainly due to interference with the hepatic synthesis of coagulation proteins) and has an overall incidence of around 5% according to recent studies. The gene discussed is ASPG; the disease is deep vein thrombosis.