FACTOR VII DEFICIENCY

SCIENTIFIC BACKGROUND

Factor VII (FVII) is a vitamin K-dependent glycoprotein that is synthesized in the liver and released into the blood. In the presence of calcium, it forms a complex with tissue thromboplastin (TF). During this process, factor VII is activated into factor VIIa. The TF-FVIIa complex then activates Factor X and Factor IX, resulting in the polymerization of fibrin in the course of the coagulation cascade.

Genetic factor VII deficiency is one of the rare congenital coagulation disorders caused by pathogenic variants in the F7 gene. The disorder is inherited in an autosomal recessive manner and has an incidence of approximately 1:300,000. Heterozygous carriers are usually asymptomatic, while homozygous or compound heterozygous carriers often develop hemorrhagic diathesis (an increased tendancy to bleed). Factor VII deficiency is characterized by a pathological prothrombin time with a normal partial thromboplastin time (PTT). Residual factor VII activity often does not correlate with the extent of bleeding tendency. The symptoms are highly variable since factor VII deficiency is not only affected by genetic factors. Environmental factors such as nutrition, diabetes, or the intake of sex hormones (in women) also modulate the phenotype.

Factor VII deficiency may also be acquired (e.g., acquired vitamin K deficiency, liver disease). Rarely, factor VII deficiency has also been described in the context of thrombophilia, which is usually associated with hyperhomocysteinemia.

Substitution therapy with concentrated FVII preparations or recombinant activated FVII is possible.

References

Sevenet et al. 2017, Clin Appl Thromb Hemost 23(7):703 / Peyvandi et al. 2012, Haemophilia 18:148 / Kogiso et al. 2011, Clin Apll Thromb Hemost 17:E205 / Herrmann et al. 2009, Haemophilia 15:267 / Herrmann et Wulff 2004, Hämostaseologie 2:94 / Perry 2002, Brit J of Haematology 118:689