Platelet factor V to the rescue.

摘要

In this issue of Blood, Duckers and colleagues show that residual platelet factor V is sufficient to promote thrombin generation and likely protects against major bleeding in patients with undetectable plasma factor V. Blood coagulation factor V (FV) plays an essential role in hemostasis and has a profound influence on the production of thrombin. Factor V deficiency (parahemophilia) is an autosomal recessive bleeding disorder first described in the 1940s by Paul Owren in Norway. Deficiency in FV presents a conundrum because the phenotype is variable and unexpectedly poorly correlates with FV levels in plasma. Patients with undetectable levels of FV(< 1%) due to homozygous nonsense, frameshift, or missense mutations exhibit the gamut of phenotypes from asymptomatic to severe bleeding. These observations make no sense considering the fundamental role played by FV in coagulation and with findings in the FV knockout mouse, which have a lethal phenotype.