A case of protein C deficiency associated with cerebral infarction and obstruction of deep leg and inferior mesenteric veins.

Protein C, a vitamin K-dependent protein, is a blood coagulation inhibitor. Its deficiency causes systemic thrombosis. A 31-year-old woman developed cerebral infarction followed by late psychomotor seizures, and thrombosis in the inferior mesenteric vein and bilateral crural veins. Her parents were first cousins. Her mother died of cerebral thrombosis in her 30's. Her elder brother died of suspected purpura fulminans immediately after birth. Her protein C activity and protein C antigen level decreased markedly and were less than 5% of those of normal controls and 0.3 microgram/ml, respectively. Her father, a paternal aunt and a maternal uncle also showed a low protein C activity and protein C antigen level. This patient seems to have congenital protein C deficiency which produced thrombosis in the leg veins and the mesenteric vein, probably cerebral infarction.