[Protein C deficiency and vascular thromboses. Apropos of 2 cases and a review of the literature].

Protein C, a physiological inhibitor of coagulation, acts by inactivating coagulation factors V and VIII. It was identified 20 years ago and purified 10 years later. Its anticoagulant properties have been confirmed by the demonstration of thromboembolic diseases associated with constitutional protein C deficiency. Deficiency is defined as a less than 65 p. 100 level of the protein. There is no correlation between protein C level and clinical severity. Constitutional protein C deficiency is transmitted as an autosomal dominant trait. The protein C level observed in homozygous deficiency is about 50 p. 100, more often quantitative (type I) than qualitative (type II), the other coagulation factors being present at normal levels. Protein C deficiency is responsible for recurrent and familial thromboembolic necrosis and for cutaneous necrosis during treatment with antivitamin K drugs. Protein C assays must now be part of the aetiological evaluation of thromboembolic disease. Physiological variations in protein C levels have been encountered in neonates and pregnant women as well as in some pathological conditions, after surgery or under certain treatments. Familial inquiries are essential to detect asymptomatic protein C deficient subjects. Treatment rests on anticoagulants: antivitamin K drugs after effective heparinization in thromboembolic accidents, prevention of accidents by heparin in protein C deficient subjects and when a risk of thromboembolic disease is present. We report here one case of venous thrombosis and one case of arterial thrombosis, both being characterized by the finding of protein C deficiency during full evaluation of haemostasis factors.