Factor VII Deficiency [D68.23]
Dipl.-Biol. Birgit Busse, B.Sc. Camilla Ladinig
Factor VII (FVII) is a vitamin K-dependent glycoprotein which is synthesized in the liver and released into the blood. In the presence of calcium it forms a complex with tissue thromboplastin (tissue factor, TF) thereby converting factor VII into its active form factor VIIa. The TF-FVIIA complex then activates factor X and factor IX which in the course of the coagulation cascade results in the polymerization of fibrin.
The genetically caused factor VII deficiency belongs to the rare inherited disorders of coagulation and is caused by mutations in the F7 gene. The disease is inherited in an autosomal recessive pattern and has an incidence of about 1 in 300,000. Heterozygous carriers are generally asymptomatic, homozygous or compound heterozygous carriers frequently develop a hemorrhagic diathesis (increased susceptibility to bleeding). A factor VII deficiency can be detected by a pathological Quick time under normal PTT. The residual factor VII activity frequently does not correlate with the susceptibility to bleeding. The symptoms of the disease are very variable as the factor VII deficiency is not only influenced by genetic factors. Environmental factors such as diet, diabetes or the intake of sexual hormones (in women) modulate the phenotype.
A factor VII deficiency may also be acquired e.g. as a result of vitamin K deficiency or liver disease. In rare cases a factor VII deficiency was described in association with thrombophilia, which frequently is accompanied by hyperhomocysteinemia.
Treatment options consist of substitution therapy with factor VII concentrate or recombinant factor VIIa.