Phenotypic Heterogeneity in Patients with Homozygous Prothrombin 20210AA Genotype. A paper from the 2005 William Beaumont Hospital Symposium on Molecular Pathology

The risk of venous thromboembolism in oral contraceptive users: the role of genetic factors-a prospective cohort study of 240,000 women in the UK Biobank

BACKGROUND

More than 150 million women worldwide use oral contraceptives. Women with inherited thrombophilia and carriers of certain thrombophilia gene variants, such as factor V Leiden and the prothrombin, are at an increased risk for venous thromboembolism, especially when combined with oral contraceptive use. Venous thromboembolism is a complex disorder involving many genetic risk factors, and recently, polygenic risk scores have been proposed to capture a significant proportion of the genetic risk of venous thromboembolism.

OBJECTIVE

The aim of this study was to estimate the risk for developing venous thromboembolism when initiating oral contraceptive use (first 2 years) and during continued use among women with a high genetic liability.

STUDY DESIGN

We used a prospective study design in which 244,420 participants from the UK Biobank were followed from birth. The effect of oral contraceptive use during the first 2 years and in the remaining years of oral contraceptive use on the risk of developing venous thromboembolism was estimated using a Cox regression with a time-dependent exposure variable. Women were stratified according to their polygenic risk scores and whether they were carriers of factor V Leiden and/or prothrombin variants.

RESULTS

When genetic risk was not considered, an increased risk for venous thromboembolism was observed during the first 2 years of oral contraceptive use (hazard ratio, 3.09; 95% confidence interval, 3.00-3.20) but not during continued use (hazard ratio, 0.92; 95% confidence interval, 0.80-1.05). However, when genetic risk was considered, women in the highest polygenic risk score category had a more pronounced risk of developing a venous thromboembolism during the first 2 years of oral contraceptive use (hazard ratio, 6.35; 95% confidence interval, 4.98-8.09), and a high risk was also observed among factor V Leiden (hazard ratio, 5.73; 95% confidence interval, 5.31-6.17) and prothrombin variant carriers (hazard ratio, 5.23; 95% confidence interval, 4.67 - 5.87). A high polygenic risk score in combination with being a factor V Leiden and prothrombin variant carrier conferred the highest risk for developing a venous thromboembolism during the first 2 years of oral contraceptive use (hazard ratio, 14.8; 95% confidence interval, 9.28-23.6). Women with a high genetic liability also had an increased risk during continued use but it was less pronounced, and the highest risk was conferred to carriers of both factor V Leiden and the prothrombin variant (hazard ratio, 4.93; 95% confidence interval, 3.16-7.7).

CONCLUSION

Evaluating polygenic risk can identify additional venous thromboembolism risk that is not captured in the commonly investigated genes for inherited thrombophilia. Our results indicate that oral contraceptive use is associated with an increased risk for developing a venous thromboembolism, particularly among women with a high genetic predisposition, and that oral contraceptive use dramatically increases the risk thereof short after initiation of use, which decreases with continued use. This suggests that the polygenic risk score could be used to identify women who are at high risk for developing a venous thromboembolism and advise them on alternative methods of contraception.

Homozygous Carriers of F2 c.20210G>A Variant: A Report of Two Cases and Literature Review

Thromboembolism is known to be a multifactorial event that is impacted by various genetic and environmental factors. The genetics society's recommended name for this variant is c.*97G>A (this is the nomenclature we need to use in the patient report). However, people have been using legacy names c.20210G>A or G20210A (so these are common names). One of the most common genetic variants associated with inherited thrombophilias, F2 c.20210G>A is acknowledged to be a weak but significant risk factor for thromboembolism. However, its clinical presentation has been described as phenotypically heterogeneous. We present two rare cases with homozygous F2 c.20210G>A variant, one of which also carries a heterozygous variant in coagulation factor V gene F5, c.1601G>A (p.Arg534Gln; commonly known as factor V Leiden). We described the clinical courses of these two cases and discussed F2 c.20210G>A and factor V Leiden as genetic risk factors in thromboembolism, the role of provoking factors, such as surgery and malignancy, and the management of such patients.

Internal Carotid Artery Dissection With Thrombosis in a Child With Prothrombin Gene Mutation

Prothrombin gene mutation (prothrombin thrombophilia) is an inherited disorder that increases the risk of venous thrombosis. However, limited data exist on the risk of arterial stroke in an at-risk population. Several meta-analyses report slightly increased risk in specific populations. We report a 10-year-old Hispanic girl who presented to the emergency department with a seizure. This seizure occurred five days after she tripped and fell without any initial associated symptoms. She had left-sided hemiparesis on physical examination after the seizure. Imaging revealed internal carotid artery (ICA) dissection with thrombus, right caudate nucleus and putamen infarcts, and ischemic penumbra. She subsequently had an endovascular thrombectomy of the right ICA with reperfusion. Genetic testing showed a prothrombin gene mutation (G20210A). Prothrombin gene mutation was the most likely explanation for her stroke in the absence of a significant risk factor for arterial thrombosis or an underlying hypercoagulable disorder. Further investigations are required to determine the risks and evaluate the correlation between prothrombin gene mutation and ischemic stroke in children.

Prothrombin Gene Mutation as a Teaching Tool: An Autobiographical Case Report

The prothrombin G20210A factor II mutation carrier status has been reported to cause complications during pregnancy. This report presents the case of a patient diagnosed with heterozygous prothrombin G20210A factor II mutation at 29 years of age during preconception genetic screening. The patient had two uncomplicated pregnancies. The patient underwent laparoscopic cholecystectomy with a complicated postoperative course. The complications included deep vein thrombophlebitis (DVT), portal vein thrombosis (PVT), and pulmonary embolization (PE). The treatment options and contraceptive choices are also discussed in this report. Our report discusses the subsequent risks inherent in a heterozygote following the administration of oral contraceptives, prolonged immobilization related to lower extremity trauma, and extended motor vehicle excursion.

Prothrombin G20210A Gene Mutation-Induced Recurrent Deep Vein Thrombosis and Pulmonary Embolism: Case Report and Literature Review

Inherited thrombophilia is an important cause of venous thrombosis. The Factor V Leiden (FVL) is the most commonly encountered mutation, followed by the prothrombin G20210A gene mutation (PTM). The typical venous thrombotic events (VTEs) associated with PTM mutations are deep vein thrombosis (DVT) and pulmonary embolisms (PE). The PTM is inherited in an autosomal dominant pattern with variable penetrance. While heterozygous PTM mutations are more frequent and well documented in the literature, rare cases of homozygous PTM mutations are also reported. In this report, we discuss a 56-year-old male with a past medical history of homozygous prothrombin gene mutation (G20210A) who presented with an unprovoked DVT of the right lower extremity involving both the proximal and distal veins associated with multiple bilateral PEs. This case is unique in terms of the homozygous PTM inheritance, the age at which the patient presented (usually presentation is earlier in life), and the fact that he had a recurrence of both DVT and PE simultaneously.

The impact of activated protein C resistance on the patency of arteriovenous grafts for hemodialysis access

INTRODUCTION

Vascular access is required for hemodialysis treatment. An effect of activated protein C resistance on access thrombosis rates has not yet been investigated. The aim of this study is to determine whether an activated protein C resistance is correlated with the patency of polytetrafluoroethylene arteriovenous grafts.

METHODS

The primary endpoint was the impact of activated protein C resistance; secondary endpoints were the influence of Factor V Leiden thrombophilia, homocysteine, ß2-glycoprotein antibodies, and other laboratory values on the assisted primary patency.

RESULTS

Forty-three grafts in 43 patients were included. The overall mean assisted primary patency was 18.4 months (±3.16 SE). Activated protein C resistance (p = 0.01) and ß2-glycoprotein antibodies (p = 0.018) had a significant influence on the assisted primary patency. The assisted primary patency for patients with low (<4) activated protein C resistance was 9.3 months compared to 24.8 of those with a high (≥4) activated protein C resistance. Patients with low (≤2.6) ß2-glycoprotein antibodies presented an assisted primary patency of 31.8 months whereas those with high (>2.6) ß2-glycoprotein antibodies showed 9.3 months. In all patients with a pathologic activated protein C resistance, a heterozygous or homozygous Factor V Leiden thrombophilia was detected.

CONCLUSIONS

This study identified low activated protein C resistance and high ß2-glycoprotein antibodies as risk factors for thrombosis in polytetrafluoroethylene arteriovenous grafts. A prospective study is needed to clarify if oral anticoagulation should be administered to all patients with a pathologic activated protein C resistance blood value and/or factor V Leiden mutation.

Genetics of suspected thrombophilia in Serbian females with infertility, including three cases, homozygous for FII 20210A or FV 1691A mutations

Reproductive failure (recurrent foetal loss, unexplained infertility and IVF implantation failure) may be, in a number of cases, explained by thrombophilia, either acquired or inherited. Several genes contribute to thrombophilia, some with major effect (Factor V, Factor II), and some with minor effect (MTHFR, PAI-1, ATIII, etc.). The aim of this study was to estimate frequency of thrombophilia-associated genotypes (FII20210G > A, FV1691G > A, MTHFR677C > T and PAI-1 -675 4G/5G) in a group of 1631 Serbian women experiencing reproductive failure, and compare it with a healthy, female control group. Our results showed marginally significant (p = 0.050) differences in allele frequencies between patients and controls for the FV1691 mutations. For the FII20210G > A, although the statistical significance was not achieved (p = 0.076), we found higher frequency of variant allele in patients compared to controls (1.87% vs. 0.38%, respectively) which may point to a possible role of this polymorphism in thrombotic events. For the MTHFR677C > T and PAI-1 -675 4G/5G, we found no difference in distributions of genotype or allele frequencies between these two groups (p > 0.05). For three subjects with very rare genotypes (two patients homozygous for FV1691G > A and one patient homozygous for FII20210G > A) we performed additional biochemical analyses for haemostasis, as well as genotyping of two polymorphisms (MTHFR1298A > C and ATIII786G > A).

Homozygous Carrier of Prothrombin G20210A Mutation with Massive Pulmonary Embolism and His Family: Gender Differences of Susceptibility to Mutation

Prothrombin 20210 G>A mutation is the second most frequent inherited factor increasing the risk for developing venous thromboembolism (VTE). The risk for VTE in homozygous carriers of this mutation is not well studied because of their rarity are rare. We report a case of a homozygous carrier of prothrombin mutation: a young man with massive pulmonary embolism, and his family - an asymptomatic homozygous sister, heterozygous parents with asymptomatic mother, and father with history of deep venous thrombosis (DVT). To our knowledge, this is the first reported case of homozygous prothrombin mutation carriers in Bulgaria and the other Balkan countries. We conclude that the homozygous prothrombin mutation creates predisposition for VTE that can manifest or not depending on additional factors, one of which could be male gender.

Hereditary thrombophilic risk factors for recurrent pregnancy loss

This review summarizes current knowledge about the role of hereditary hypercoagulation factors predisposing to thrombophilia-associated recurrent fetal loss. Thrombophilias are a major cause of adverse pregnancy outcome, playing a role in the etiology of up to 40% of cases worldwide. Hereditary thrombophilic predispositions to recurrent pregnancy wastage include genetic lesions in blood coagulation factors II and V as well as natural anticoagulants antithrombin, protein C, and protein S. Furthermore, methylenetetrahydrofolate reductase gene variants conferring higher thrombophilia risk in combination with these mutations and the newly described annexin A5 gene M2 promoter allele are associated with repeated fetal loss. The review gives a concise description of the molecular defects arising from the genetic changes, of the role these factors play in the timing and definition of fetal loss, and risk estimates from available studies and meta-analysis. This knowledge is instrumental for a more precise assessment of individual risks for repeated fetal loss and should guide therapeutic strategies, where relevant. Since the average childbearing age increases in Western societies, the importance of a timely diagnosis of fetal loss predisposition is increasing.

The factor V G1691A, factor V H1299R, prothrombin G20210A polymorphisms in children with family history of premature coronary artery disease

Atherosclerosis, the major cause of coronary artery disease (CAD), has a very long asymptomatic development phase, which begins in childhood. In this study, we describe the factor V G1691A, factor V H1299R and prothrombin G20210A gene polymorphisms in children with a family history of premature CAD. Evidence of these polymorphisms in these children may predict the probability of having atherosclerosis in the future. Our study included a total of 140 children, 72 males and 68 females between the ages of 4.9 and 15.7 years. Among these children, 73 had a parental history of premature CAD and the remaining 67 belonged to our control group. The participants were screened for the mutations factor V G1691A, factor V H1299R and prothrombin G20210A by polymerase chain reaction amplified DNA products with specific oligonucleotide probes. Our results suggested that frequencies of the mutated allele of factor V G1691A and prothrombin G20210A are higher in children with a parental history of premature CAD. In conclusion, factor V G1691A and prothrombin G20210A polymorphisms which were detected in higher frequencies in children with a parental history of premature CAD may indicate a risk for developing atherosclerosis and might be useful in screening for CAD in children; however, large population-based research is necessary to investigate further genetic risk assessment for CAD.

Thrombotic genetic risk factors and warfarin pharmacogenetic variants in São Miguel's healthy population (Azores)

SUMMARY

BACKGROUND

The Azorean population presents the highest standardized mortality rate for cardiovascular diseases (CVD) when compared to mainland Portugal and other populations. Since thrombosis is a common cause of CVD, we assessed four polymorphisms in three thrombotic risk genes - F5 (G1691A), F2 (G20210A) and MTHFR (C677T, A1298C), in 469 healthy blood donors from São Miguel Island (Azores). We also analysed the CYP2C9 (C430T, A1075C) and VKORC1 (G1639A) variants in fifty-eight individuals with predisposition to thrombosis (possessing at least one variation in F5 or F2 genes and one in MTHFR) to evaluate their warfarin drug response genetic profiles.

RESULTS

Among the 469 individuals, the data showed that thrombotic risk allele frequencies - 1691A (4.9%), 20210A (1.8%), 677T (41.7%) and 1298C (24.8%) - were similar to other Caucasians, but significantly different from mainland Portuguese (chi2, p < 0.001). The combined analysis of these variants identified twenty-two different genetic profiles (genotype order: F5, F2, MTHFR C677T and A1298C). Complete homozygosity for all wild-type alleles (GG GG CC AA) was present in 11.7%, being GG GG CT AA (22.4%) the most frequent profile. The results also demonstrated that 12.4% (58 out of 469) of São Miguel islanders have increased genetic predisposition to thrombosis. Subsequently, we evaluated these individuals for their warfarin response genetic profiles. The data showed that seven out of fifty-eight individuals are poor metabolizers (two with CYP2C9*2/*2 and five with CYP2C9*2/*3 genotypes). VKORC1 polymorphism analysis identified twelve individuals (20.7%) with AA genotype, who probably will require lower doses of warfarin. The joint analysis of CYP2C9 and VKORC1 revealed that 79.3% (46 out of 58) of the individuals carry at least one polymorphism in these genes. Within these, twenty-five individuals (43.1%) need intermediate and/or low doses of warfarin, if treatment is started.

CONCLUSION

The present study demonstrated, for the first time, that São Miguel, and possibly the Azores population, shows significant differences on allele frequencies of thrombotic risk factors when compared to mainland Portugal. This research constitutes a primary approach for future studies on CVD, as well as for the implementation of warfarin dosing protocols using the patient's genotypic information.

Different outcome of six homozygotes for prothrombin A20210A gene variant

Prothrombin G20210A gene variant (FII G20210A) is a risk factor for venous thrombotic disease while conflicting results have been reported for the risk of arterial thrombotic events. However, vascular episodes were absent in up to 40% of the 67 homozygotes for the G20210A described so far, which indicates that the clinical expression depends on additional risk/trigger factors. We describe six homozygotes for the G20210A variant, among which the first pair of siblings (cases n. 3 and 4) reported so far that displayed a strongly heterogeneous clinical outcome. Case 1, a female of 27 years, developed a full thrombosis of common femoral, superficial and popliteal veins. She assumed oral contraceptives in the last two years. Case n. 2, 34 years old, suffered of recurrent pregnancy loss in absence of any causative alteration. Cases n. 3 and n. 5 experienced arterial thrombotic disease, i.e., juvenile myocardial infarction (40 years old) and stroke (48 years old), respectively, in absence of other risk factors. Finally, cases n. 4 and 6 identified as homozygotes for the FII G20210A variant being consanguineous of symptomatic subjects bearing the variant, did not experience any episode of venous nor arterial disease. Both of them have chronic liver disease with an impairement of the prothrombin time INR. Thus, homozygotes for the G20210A are at risk for arterial (in addition to venous) thromobotic events; chronic liver disease might modulate this risk.

Genetic variations and their influence on risk and treatment of venous thrombosis

Venous thrombosis (VT) is a highly prevalent disease. Risk factors can be genetic or acquired. The well-established genetic polymorphisms predisposing to thrombophilic disorders can be divided into rare 'loss-of-function mutations' in anticoagulant proteins and common 'gain-of-function mutations' in procoagulant proteins, which are weaker risk factors. In addition to functional polymorphisms, defects in common pathways affecting biosynthesis or clearance of plasma coagulation factors and their relations to VT risk have been detected. Recently, investigations regarding genetic variations and response to drug treatment, relevant for the pathogenesis as well as therapy of venous thromboembolism have been performed. The methodical advances in genetic research have led to the identification of a number of new variants with still unclear association to VT. This review aims to discuss the established genetic risk factors as well as some candidate predictors of VT. Further, the recent developments in pharmacogenomics are reviewed.