Five days after starting warfarin therapy in a patient of atrial fibrillation the 60 year old man returns to his physician complaining of large patches of discolored stain over his gluteal region and legs.This complication is most likely the result of:
a. Antithrombin III deficiency
b. Protein C deficiency
c. Drug allergy
d. Very high INR
b. Protein C deficiency
Protein C is a vitamin K-dependent plasma protein that, when activated, helps to inactivate factors Va and VIIIa, thereby regulating blood clotting. Warfarin therapy initially decreases protein C levels faster than other clotting factors, which can lead to a pro-coagulant state and increase the risk of skin necrosis or large patches of discoloration. This is often referred to as warfarin-induced skin necrosis and can be exacerbated in patients with an underlying protein C deficiency.