Protein C Deficiency Resulting From Possible Double Heterozygosity and Its Response to Danazol

A unique family with protein C (PC) deficiency is described. The proband had a history of renal vein thrombosis as a newborn and iliofemoral thrombosis at the age of 6 years. After 6 months of heparin treatment. discontinuation of anticoagulation therapy was accompanied by persistent hypofibrinogenemia with increased fibrinogen consump-tion. With continuous infusion of heparin. fibrinogen turn-over normalized, and the child has remained free of throm-bosis. Both the immunologic level of PC and the functional activity measured by amidolytic assay were moderately reduced (47 % and 34%. respectively). Functional activity of PC measured by its anticoagulant activity was dispropor-tionately lower (14%). A 3-year-old asymptomatic sibling had a similar disproportionate reduction of PC anticoagu-lant activity compared with the amidolytic activity o