A patient with deep vein thrombosis is started on warfarin without heparin bridging. On day 3, he develops painful purpuric skin lesions on the thighs and buttocks that progress to necrosis. Which deficiency predisposes to warfarin-induced skin necrosis?

• A Factor XIII deficiency
• B Factor VIII deficiency
• C Protein C deficiency ✓
• D Antithrombin III deficiency

Explanation

Protein A has a short half-life (6-8 hours). When warfarin is started without heparin bridging, protein A levels drop before the vitamin K-dependent procoagulant factors (II, IX, X), creating a transient hypercoagulable state that causes microvascular thrombosis in subcutaneous fat. Factor VIII, XIII, and antithrombin III deficiencies do not cause this phenomenon.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.