Deficiency ofProtein C in Congenital Thrombotic Disease

thrombosis was studied to determine if a plasma pro-tein deficiency could account for the observed dis-ease. Protein C levels in plasma were determined immunologically using the Laurell rocket technique. The propositus, his father, and his paternal uncle, who are severely affected, had 38-49 % of normal levels of protein C antigen, whereas unaffected family members had normal levels. There was no familial deficiency of antithrombin III and plasminogen. Be-cause activated protein C is a potent in vitro anti-coagulant enzyme and an in vivo profibrinolytic agent, it is suggested that the recurrent thrombotic disease in this family is due to an inherited deficiency in pro-tein C