A case of nephrotic syndrome with pulmonary embolism due to acquired antithrombin iii deficiency: Treatment with plasma derived antithrombin iii and low molecular weight heparin.

Background: The pro-coagulable state in nephrotic syndrome is due to urinary losses of anti-coagulant proteins, including antithrombin III. Low molecular weight heparin (LMWH) is a common initial treatment for thrombosis and works by activating anti-thrombin III that itself inhibits factor Xa. In thrombosis in nephrotic syndrome, antithrombin levels are only infrequently checked and replacement is uncommon. We describe a case of thromboembolism due to an acquired antithrombin III deficiency and treatment with plasma derived anti-thrombin III (Thrombotrol-VF CSL ltd Australia) and LMWH. Case report: A 21-year-old male with focal segmental glomerulosclerosis, previously managed with rituximab, presented with a relapse of his nephrotic syndrome involving severe oedema and ascites, serum albumin <6 g/L, total cholesterol 17 mmol/L, UPCR 1.99 g/mmol, and right sided chest pain. A perfusion scan confirmed a large right segmental pulmonary embolus. He was commenced on intravenous methylprednisolone and rituximab and later cyclosporin. Given his impaired gut absorption and significant clot burden, his thromboembolism was treated with therapeutic enoxaparin. His initial anti-Xa and anti-thrombin III levels were low at 0.30 IU/mL (target range 0.50-1) and 0.29 IU/mL (normal 0.8-1.20) respectively. To ensure efficacy of LMWH he received Thrombotrol-VF with daily monitoring and replacement to achieve target levels. Owing to urinary losses, his anti-thrombin III levels were intermittently low even after achieving therapeutic anti-Xa levels. He was transitioned to warfarin once his gut absorption improved, evidenced by therapeutic oral cyclosporin drug levels and later his INR. Conclusion(s): Anti-thrombin III losses in severe nephrotic syndrome should be considered when treating its thrombotic complications. When using LMWH it may be prudent to check anti-thrombin III levels and replace as needed.