We report a case of a 6-year-old girl with severe protein S deficiency due to a homozygous mutation and recurrent episodes of skin necrosis. She developed purpura fulminans at birth and a catheter-related venous thrombosis complicated by massive pulmonary embolism at the sixth day of life. Long-term oral anticoagulant therapy with a vitamin K-antagonist was started with a therapeutic range of the international normalized ratio of prothrombin time between 2.0 and 3.0. Unfortunately, this common range was not sufficient because recurrent episodes of warfarin-induced skin necrosis developed if the international normalized ratio was <4.0. Vitamin K antagonists decrease plasma level of vitamin K–dependent coagulation proteins, including the natural anticoagulant protein C. In our patient, the hypercoagulable state due to warfarin-induced reduction of protein C, other than severe protein S deficiency, outweighed the anticoagulant efficacy of the inhibition of procoagulant factors II, VII, IX, and X. The switch of anticoagulant therapy from warfarin to rivaroxaban, a direct inhibitor of activated factor X that does not inhibit other vitamin K–dependent proteins, resulted in the disappearance of skin necrosis at 1 year of follow-up. Rivaroxaban may be considered as a valid anticoagulant alternative in patients with severe inherited protein S deficiency and warfarin-induced skin necrosis.
Anticoagulant Treatment With Rivaroxaban in Severe Protein S Deficiency
FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose.
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Ida Martinelli, Paolo Bucciarelli, Andrea Artoni, Emilio F. Fossali, Serena M. Passamonti, Armando Tripodi, Flora Peyvandi; Anticoagulant Treatment With Rivaroxaban in Severe Protein S Deficiency. Pediatrics November 2013; 132 (5): e1435–e1439. 10.1542/peds.2013-1156
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