Livedo Vasculitis With Protein C System Deficiency

To the Editor.— Protein C is a vitamin K—dependent plasma glycoprotein synthetized in the liver. Thrombomodulin (the endothelial receptor for thrombin) catalyzes the thrombin activation of protein C. Activated protein C has anticoagulant activity. Protein C deficiency is responsible for a hypercoagulable state that can be symptomatic. 1 Protein C deficiency is either acquired or is transmitted in an autosomal dominant fashion. 1 Homozygous deficiency is responsible for neonatal purpura fulminans and disseminated intravascular coagulation within the first days of life. Heterozygous deficiency is responsible for deep-vein thrombosis in young adults. Development of skin necrosis in these patients during the initiation of oral anticoagulant therapy is also well known. It is probably caused by a rapid drop in protein C concentration, which has a shorter life than most of the procoagulant vitamin K—dependent factors, thus resulting in a transient hypercoagulable state. We report a case of livedo reticularis with superficial