Warfarin-induced skin necrosis classically occurs between days 3 and 7 of therapy in patients with an inherited deficiency of:
- A Antithrombin III
- B Factor XIII
- C Protein C or protein S ✓
- D Alpha-2 antiplasmin
Correct answer: C. Protein C or protein S
Explanation
Warfarin lowers all vitamin K-dependent proteins, but proteins B and S have shorter half-lives than factors II, IX and X. A transient hypercoagulable window therefore precedes full anticoagulation, and patients with pre-existing protein B or S deficiency develop microvascular thrombosis in subcutaneous fat, presenting as skin necrosis. Antithrombin deficiency causes heparin resistance rather than warfarin necrosis.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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