A Fatal Thrombotic Disorder Associated with an Acquired Inhibitor of Protein C

PROTEIN C is a vitamin K-dependent anticoagulant protein that inactivates the coagulation cofactors Va and VIIIa in a reaction that is enhanced by phospholipid and protein S.1 2 3 In order for protein C to serve as an anticoagulant, it must be activated by the thrombin–thrombomodulin complex to form activated protein C.4 A deficiency of protein C has been reported to be associated with recurrent venous thrombosis5 and warfarin-induced skin necrosis.6 A total lack of protein C in infants is associated with purpura fulminans neonatalis7 and massive thrombosis.8 We report a fatal thrombotic disorder in a patient with an IgG paraprotein who . . .