Warfarin induced skin necrosis

Warfarin induced skin necrosis is often heralded by paresthesia, or a sensation of pressure, associated with an erythematous flush that is usually poorly demarcated. The lesions are painful, sudden, well localized and initially hemorrhagic or erythematous. In women, the site of the lesion is random and unpredictable, but the breast is the most common site, followed by the buttocks and thighs. Occasionally, the trunk, face and extremities are also involved.

The mechanism is thought to be that, following the initiation of warfarin, both protein C antigen and activity levels drop rapidly, compared with levels of other vitamin K-dependent factors such as factors IX and X, and prothrombin. This observed rapid early fall in protein C level prompted the hypothesis that the administration of warfarin to protein C-deficient individuals causes a temporary exaggeration of the imbalance between pro- coagulant and anticoagulant pathways; that is, the early suppressive action of warfarin on protein C may not be counterbalanced by the anticoagulant effect created by the decline in other vitamin K-dependent factors, thereby leading to a relative hypercoagulable state at the start of treatment. This leads to thrombotic occlusions of the microvasculature with resulting necrosis.