Clinical Findings: Vitamin K antagonists have been shown to cause a specific type of cutaneous eruption known as warfarin necrosis, which occurs in approximately 0.05% of patients taking the medication. Warfarin necrosis affects the areas of the body that have increased body fat, such as the breasts, the abdominal pannus, and the thighs. The feet are also particularly prone to development of warfarin necrosis. The skin initially develops small, red to violaceous petechiae and macules preceded by paresthesias. These regions become erythematous and purple (ecchymoses) with intense edematous skin. The lesions eventually ulcerate or form hemorrhagic bullae. The hemorrhagic bullae desquamate, leaving deep ulcers. Painful cutaneous ulcers may occur, with some extending into the subcutaneous tissue, including muscle. Most ulcers appear within 5 to 7 days after the initiation of warfarin therapy. Secondary infection may be a cause of significant morbidity. The affected areas continue to undergo necrosis unless the warfarin is withheld and the patient is treated with a different class of anticoagulant. The feet and lower extremities may have a reticulated, purplish discoloration called “purple toe syndrome.” This cutaneous drug reaction can be eliminated or at least drastically decreased if the patient is pretreated with heparin or another equivalent anticoagulant before warfarin is initiated.
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