A 60-year-old man with nephrotic syndrome (albumin 1.8 g/dL) due to membranous nephropathy presents with acute-onset right leg swelling and pain. Doppler confirms deep vein thrombosis. Which underlying mechanism BEST explains his thrombotic risk?
- A Urinary loss of antithrombin III ✓
- B Antiphospholipid antibody syndrome
- C Polycythaemia secondary to erythropoietin excess
- D Acquired protein C deficiency alone
Correct answer: A. Urinary loss of antithrombin III
Explanation
Nephrotic syndrome causes urinary loss of antithrombin III, protein S, and other anticoagulant factors, predisposing to venous thromboembolism. Renal vein thrombosis and DVT are classic complications, especially in membranous nephropathy. Antiphospholipid syndrome is unrelated to nephrotic proteinuria. Polycythaemia is not a feature of nephrotic syndrome. Protein C loss contributes but antithrombin III loss is the dominant prothrombotic mechanism.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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