Secondly, resistance to activated protein C as a result of factor V Leiden is associated with thromboembolic disease at an early age (Price DT, Ridker PM.Ann Intern Med.1997;127:895-903).
In addition, mild and moderate hyperhomocysteinaemia and Factor V Leiden (FVL; Arg506Gln) have recently been identified as thrombotic risk factors.FVL. which renders resistance to activated Protein C, is the most common inherited genetic risk factor for thrombosis with a high allelic frequency amongst Caucasians.
In unadjusted analyses, clinically important associations were observed between factor V Leiden and venous thrombosis, hyperhomocysteinemia and arterial thrombosis, and activated protein C resistance (APCR) and venous thrombosis (OR, 95% CI = 4.00, 1.35-11.91; 4.79, 2.03-11.33; and 2.03, 1.03-3.97, respectively).
The diagnosis of factor V Leiden thrombophilia is established in a proband by identification of a heterozygous or homozygous c.1691G>A variant (referred to as the factor V Leiden variant in <i>F5</i>, the gene encoding factor V) in conjunction with coagulation tests such as the APC resistance assay.
Hemostaseological function tests demonstrated a pathologic activated protein c resistance and PCR analysis a heterozygous defect of the factor V (Leiden).
This reduction in APC-R ratio was not explained by (1) the presence of the factor V Leiden, found in only one of 165 patients with SS disease including those tested for APC-R, or (2) the presence of lupus anticoagulants.
Laboratory tests revealed a pathologic activated protein C resistance and a reduced functional protein S. The underlying genetic defect was identified as a heterozygous coagulation factor V mutation.
A point mutation in coagulation factor V (factor V Leiden) results in resistance to activated protein C and probably represents the most common genetic risk factor for venous thrombosis.
The factor V Leiden (FVL) mutation, causing resistance to activated protein C, has recently been recognised as the most important genetic thrombophilia in the Western population.
Acquired activated protein C resistance (aAPCR), not associated with factor V Leiden, has been described in cancer patients with an increased risk of venous thromboembolism (VTE).
Thrombophilia was suspected and the relative investigation revealed high levels of factor VIII procoagulant, which is frequent in hemodialysis patients, and resistance to activated protein C. Polymerase chain reaction detected that the patient was heterozygous for factor V Leiden, which is quite common in general population.
Evidence against heterozygous coagulation factor V 1691 G-->A mutation with resistance to activated protein C being a risk factor for coronary artery disease and myocardial infarction.
In the 5 years that have elapsed since initial identification of these individuals, resistance to activated protein C (APC resistance), which is associated with the factor V Leiden gene mutation, has emerged as an important and highly prevalent inherited thrombophilic risk factor.
A case-control study was carried out to evaluate the prevalence of APC resistance and factor V Leiden in patients with retinal vein occlusion (RVO) and in control subjects.
Activated protein C resistance was measured in all subjects and factor V Leiden genotype testing was performed in those individuals with phenotypic activated protein C resistance.