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Factor V Deficiency - F5

Leiden Mutation

Clinical Features

Thromboembolic events may be acquired or inherited. Rare defects in the antithrombin III gene, protein S gene and protein C gene have a prevalence of less than 1%. The genetically determined resistance of coagulation factor V against activated protein C (APC resistance) shows a higher prevalence. The mutation in the factor V gene disturbs the inactivation of protein C by factor V leading to hypercoagulation.

Heterozygosity for the factor V mutation is present in around 5% of the population and increases the risk for thrombosis by 5 to 10 times. Homozygosity (only in around 0.05-0.5% of the population) increases the risk by 50 to 100 times.

Additional susceptibility factors such as smoking, exsiccosis or hormonal contraception are to be avoided. Drug-based antithrombotic prophylaxis is advisable if further risk factors are present such as immobilisation, pregnancy or other diseases affecting the coagulation system (e.g. prothrombin gene, MTHFR gene).

Genetic Information

The Factor V gene (F5)  is located on chromosome 1 (1q23). The factor V Leiden mutation is a point mutation at nucleotide position 1691 (G-> A) which results in the amino acid exchange Arg506Gln.

Prevalence

Heterozygosity: 1 : 200 to 1 : 20 for the European population.

Diagnostic