Warfarin-induced skin necrosis: report of four cases.

Four cases of warfarin-induced skin necrosis are reported, and previous reports of this adverse drug reaction are summarized. A 53-year-old man experienced two episodes of skin necrosis on his left flank and buttock, following the initiation of warfarin therapy for acute thrombophlebitis and after a dose adjustment. The lesion formed multiple hemorrhagic bullae that ruptured, and an eschar formed that did not heal and eventually required skin grafting. Seven days after the initiation of warfarin therapy, an area of erythema surrounded by a halo was noted on the left thigh of a 79-year-old woman. Following the typical pattern, the erythematic area turned to a blue-black color and rapidly formed an eschar deep into the subcutaneous tissue that required debridement. A 70-year-old man was given a warfarin dose of 10 mg daily that was reduced to 2.5 mg daily. It was discontinued when bullous violaceous lesions were discovered on his lower left leg and foot. His prothrombin times never exceeded 20 seconds with a control of 10.6 seconds. A 37-year-old woman was admitted with an erythematous area on her right thigh that turned blue-black and subsequently formed an eschar. Her prothrombin time was 21 seconds with a control of 10.6 seconds. Of the 50 reports of warfarin-induced skin necrosis in the literature (including the four here), 74% of the cases involved women. The mean age of the patients was 54 years, and 60% of the lesions occurred on the thigh, breast, or buttock. Usually the onset of the lesion was noted on days 3--5 of warfarin therapy. Sixty percent of the patients were hypocoagulated. The etiology of warfarin-induced skin necrosis has not been definitively established. In the event of this unusual complication, warfarin therapy should be discontinued, vitamin K should be administered to reverse the effects of warfarin, and heparin should be used to provide anticoagulation.