Warfarin-Induced Skin Necrosis

Warfarin-induced skin necrosis is a clinical–pathologic condition that arises in patients treated with vitamin K antagonists and that produces an activated blood coagulation state. The condition becomes manifest as a result of the relative loss of the protein C and S anticoagulation system in vivo. If not recognized and treated it can progress to skin mutilation, limb necrosis, and death.

Its major treatment is prevention by understanding the pharmacologic effects of vitamin K antagonists. Although first recognized in association with physician administration of warfarin without parenteral anticoagulant coverage in patients with thrombosis, it is now most commonly seen in patients who are transitioned to warfarin while having acquired protein C deficiency, as in heparin-induced thrombocytopenia thrombosis syndrome (HITTS).

Clinical Presentation

Warfarin skin necrosis is the onset of a major necrotic lesion on the skin within 24 to 72 hours after ingestion of oral vitamin K antagonists (warfarin). It can also be seen with other vitamin K antagonists (4-hydroxycoumarin derivatives, e.g., brodifacoum, difenacoum). It can affect soft tissues in the abdomen, limbs, breasts, and buttocks. It can occur as an apparent isolated event in a patient being treated for venous thromboembolism (VTE) or in other conditions associated with an activated blood coagulation state, such as HITTS, disseminated intravascular coagulation (DIC) from any etiology, or antiphospholipid syndrome.

The skin lesions are retiform purpura that consists of branching purpuric lesions caused by a complete blockage of blood flow in the dermal and subcutaneous vasculature. In addition to an activated blood coagulation state, these lesions can be seen in less common conditions such as snake bite, frostbite, cholesterol embolization, cryoglobulinemia, Neisseria sepsis, and calciphylaxis in the kidney failure patient. These patients are at high risk for VTE, and they can present with additional symptoms and signs of venous thrombosis.

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