Congenital protein c deficiency and myocardial infarction: Concomitant factor VII hyperactivity may play a role in the onset of arterial thrombosis

A 29-year-old man with congenital protein C deficiency and acute myocardial infarction is reported. Four hours after the onset of chest pain, he was treated intravenously with tissue-type plasminogen activator. Subsequent coronary angiography revealed only slight stenosis of the left anterior descending coronary artery without any atherosclerosis. The propositus, his brother, and his mother, showed low levels of both protein C activity and antigen, while plasma thrombomodulin levels were normal. His grandfather had died from acute myocardial infarction at 38 years of age. We investigated several other risk factors for arterial thrombosis, including factor VII, fibrinogen, heparin cofactor II, lipoprotein (a), and anticardiolipin antibodies. No other haemostatic abnormalities apart from factor VI hyperactivity were detected in this family. To study the effects of protein C and factor VI on procoagulant activity, prothrombin time was measured after the addition of activated protein C and factor VI to protein C-deficient plasma. The prothrombin time ratio decreased along with an increase in the factor VII level. It also decreased with a decrease in the activated protein C level. These findings indicated that the procoagulant activity of factor VI was enhanced by low protein C levels, suggesting that concomitant factor VII hyper-activity may cause acute myocardial infarction in patients with protein C deficiency.