[Protein C deficiency--a risk factor for venous thrombosis].

Protein C is a vitamin K-dependent protein which is produced in the liver. Activated protein C has an anticoagulant effect by inactivating the clotting factors V and VIII. We report on a young female patient who suffered from recurrent thrombosis of the deep calf and pelvic veins with pulmonary embolism. Superficial thrombophlebitis also occurred repeatedly. In the plasma of this patient we found reduced levels of protein C antigen (0.62 U/ml) and activity (0.42 U/ml). Investigation of other family members revealed a protein C deficiency in her father, sister, and son. During the anticoagulant treatment with Marcumar the patient developed a coumarin-induced skin necrosis, to which complication a protein C deficiency is evidently predisposed. This complication could only be prevented if heparin was given simultaneously during the adjustment period.