This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bleeding Disorders, Subject name: Pathology
Warfarin skin necrosis is caused by- 
Select and explain. 
A. Protein C/Protein S deficiency, B. APLA, C. Vitamin K deficiency, D. Fibrinogen deficiency
A: Protein C/Protein S deficiency
Answer: A: Protein C/Protein S deficiency 
Explanation: Ans. (a) Protein C/Protein S deficiency(Ref: Wintrobe's 12th/pg 1490)Warfarin skin necrosisDue to warfarin-induced rapid reduction in protein C levels in patients with a pre-existing inherited protein C deficiency that results in a hypercoagulable state and thrombosis.Not all heterozygous protein C-deficient patients receiving warfarin experience this complication, and not all patients with this complication have protein C deficiency.