Combined Factor V and Factor VIII Deficiency
FV deficiency can be confused with F5F8D, since both disorders are inherited as autosomal recessive diseases and are characterized by prolonged PT and aPTT assays. In contrast, FVIII deficiency (hemophilia A) can be distinguished from F5F8D by the X-linked inheritance (males are affected and females are usually carriers) along with the normal PT among individuals with hemophilia A. Therefore, assays of FV and FVIII are mandatory for making a diagnosis of F5F8D. The concordant reduction of FV and FVIII coagulant activity levels is also characteristic for the presence of F5F8D.
Particular attention should be paid to the possible concomitant presence of an inherited FV deficiency associated with mild hemophilia A, as such patients have the same patterns of bleeding symptoms as those with F5F8D and should be treated to increase both plasma FV and FVIII levels. Distinguishing between these two patient populations requires genetic analysis in addition to specific assays that measure coagulant activity of both FV and FVIII.Next