Ischemic venous thrombosis caused by a distinct disturbance of the extrinsic clotting system.

Abstract

Ischemic venous thrombosis that led to necrosis of four toes developed in an 81-year-old man. Despite the extensive thrombosis, results of blood clotting tests showed an extremely low prothrombin time (20%). Plasma mixing studies demonstrated an inhibitor that may have features in common with the lupus anticoagulant. Lupus anticoagulant also simulates hemorrhagic diathesis in vitro, whereas in vivo it is associated with thrombosis and thromboembolism. In contrast to the lupus anticoagulant, the inhibitor found in this patient was active within the extrinsic clotting system. Systemic steroids led to rapid clinical resolution paralleled by normalization of the prothrombin time and disappearance of the inhibitor.