Coumarin skin necrosis: a severe complication of oral anticoagulation

A 39-year-old white female with severe peripheral arterial disease, due to fibromuscular dysplasia, developed coumarin-induced skin necrosis. Owing to recurrent arterial thromboses, including one episode which resulted in left above-knee amputation, phenprocoumon therapy was initiated, at doses of 15, 9 and 3 mg on the first, second and third days of treatment, respectively. This treatment overlapped with a continuous intravenous infusion of heparin that was adjusted to aPTT levels of 1.5 to 2.5 times the normal range. On the third day of treatment she had an international ratio (INR) 4.5 (normal therapeutic range 2–4.5); the protein C level was below 5%. Heparin therapy was then stopped. Twenty-four hours later she developed severe pain of the left thigh, above the site of the amputation, associated with extensive erythema. Another 24 hours later, petechial hemorrhages had developed (Panel A) and were rapidly followed by necrosis (Panel B). Oral anticoagulation was discontinued and