[A sporadic case of protein C deficiency].

A congenital deficiency of protein C (PC) is reported in a 42-year-old male, suffering from his first spontaneous episode of deep venous thrombosis in the left lower limb. The only defect found in laboratory assays for hemostasis and hepatic function was half normal level of PC, measured by both immunological and functional assays. To confirm congenital PC deficiency, the functional activity levels of PC were compared with those of other vitamin K-dependent factors during stabilized anticoagulant therapy under stable conditions. Although the patient's father had a history of a cerebral vascular accident, his PC level was found to be within normal levels. The patient's mother, free from thromboembolic events, also had a normal PC level. So the patient seemed to be a sporadic case. However, the patient's 14-year-old son, who has been asymptomatic to this time, has the same PC deficiency state.