Lack of efficacy of low molecular weight heparin in a boy with congenital nephrotic syndrome

SUMMARY: The congenital nephrotic syndrome (CNS) is characterized by severe proteinuria, followed by hypoalbuminaemia and hypercoagulopathy. the boy was born in the 39th gestational week (1980 g bodyweight). In the first days of his life, he developed proteinuria and oedema, and on the 10th day, a thrombosis of the vena cava inferior was diagnosed. the boy was treated with unfractionated heparin, antithrombin concentrates and a low-dose of recombinant tissue plasminogen activator (rtPA). After 2 days, a complete resolution of the thrombus was observed. Treatment with unfractionated heparin and antithrombin III was continued. At the age of 3 months, low molecular weight heparin (LMWH) was started before the patient was discharged. Despite a high dose of LMWH, 250 IU/kg bodyweight, the anti-Xa-activity was always below 0.1 U/mL. Therefore, anticoagulation was achieved by the administration of vitamin K antagonist. Low molecular weight heparin is bound to albumin and antithrombin. Therefore, the renal loss of these proteins may result in low plasma levels of LMWH, and may not be effective in patients with CNS.