Combined factor V/VIII deficiency: A case report including levels of factor V and factor VIII coagulant and antigen as well as protein C inhibitor

Comprehensive coagulation studies were performed on members of a family with combined factor V/VIII deficiency. The purpose of these studies was to investigate the hypothesis that combined factor V/VIII deficiency is due to a lack of the inhibitor to activated protein C. The analyses performed included routine APTT and PT, factor V and VIII coagulant activity and antigen levels, van Willebrand factor levels, protein C antigen assay, and both protein C inhibitor activity and antigen levels. Three of the 19 family members studied were found to have a deficiency of both factors V and VIII. These three individuals showed prolonged APTTs and PTs and decreased levels of factor V and factor VIII coagulant activity and antigen. Factor VIII related antigen and ristocetin cofactor (von Willebrand factor) levels were normal. Protein C and both protein C inhibitor activity and antigen levels were also found to be normal. These findings confirm the results of other recent investigators and indicate that the autosomal, inherited combined factor V/VIII deficiency is not due to a protein C inhibitor deficiency. The real defect in this combined deficiency remains to be determined.