Selective testing for thrombophilia in patients with first venous thrombosis: results from a retrospective family cohort study on absolute thrombotic risk for currently known thrombophilic defects in 2479 relatives

Thrombotic risk and features of patients with inferior vena cava agenesis: a multicentre, retrospective, observational study

BACKGROUND

Inferior vena cava agenesis (IVCA) is a rare anomaly predisposing affected people to lower-limb venous thrombosis with low frequency of pulmonary embolism. Antenatal thrombosis and inherited thrombophilia have been suggested as causes of IVCA. However, there is little evidence on the clinical course and management of this condition. We designed a patient registry to assess the thrombotic risk and features of IVCA.

METHODS

In this this multicentre, retrospective, observational study, we included patients with IVCA diagnosed by routine imaging from 20 hospitals in Spain (n=18), Portugal (n=1), and Italy (n=1). Patients were identified from a systematic search in radiology databases using data extraction software (cohort A) and alternative searches in medical records for confirmed IVCA (cohort B; option allowed when systematic approaches were unapplicable). Primary outcomes were clinical and imaging features, thrombotic risk, phenotype of IVCA-associated thrombosis, anticoagulant treatment, and the results of thrombophilia testing.

FINDINGS

We included patients with IVCA diagnosed by routine imaging studies done between Jan 1, 2010, and Dec 31, 2022. In the systematic search, 4 341 333 imaging exams were screened from the radiology databases of eight centres. 122 eligible patients were enrolled in cohort A. A further 95 patients were identified by screening medical records at 12 centres, of whom 88 were eligible and included in cohort B, making a combined cohort of 210 patients. 96 (46%) of 210 patients were female and 200 (95%) were European or Hispanic. 60 (29%) of 210 patients had hepatic IVC interruption, whereas 150 (71%) had extrahepatic IVCA. In cohort A, 65 (53%) of 122 patients had venous thrombosis, with an estimated annual risk of 1·15% (95% CI 0·89-1·46). Extrahepatic IVCA was associated with a greater risk of venous thrombosis than hepatic IVCA (56 [67%] of 84 patients vs nine [24%] of 38 patients, odds ratio 5·31, 95% CI 2·27-12·43; p<0·0001). Analysis of 126 patients with venous thrombosis pooled from cohorts A and B showed early-onset (median age 34·6 years, IQR 23·3-54·3) and recurrent events (50 [40%] of 126 patients). Patients with extrahepatic IVCA had greater proportions of lower-limb venous thrombosis (95 [87%] of 109 vs nine [53%] of 17, p=0·0010) and recurrence (48 [44%] of 109 vs two [12%] of 17, p=0·015), but lower rates of pulmonary embolism (10 [10%] of 99 vs four [33%] of 12, p=0·044) than did patients with hepatic IVCA. 77 (63%) of 122 patients with thrombosis underwent indefinite anticoagulation. 32 (29%) of 111 patients (29 [34%] of 86 with thrombosis) had coexisting thrombophilias. The recurrence risk was lower for patients receiving indefinite anticoagulation (adjusted odds ratio 0·24, 95% CI 0·08-0·61; p=0·010), and greater for thrombophilias (3·19, 1·09-9·32; p=0·034).

INTERPRETATION

This evaluation of a large patient cohort demonstrates the high thrombotic burden of IVCA. We have identified two distinct forms of IVCA, hepatic and extrahepatic, suggesting different underlying mechanisms. Beyond clinical characterisation, we draw attention to this orphan disease and highlight the need for its study and improved care.

FUNDING

Spanish Society of Thrombosis and Haemostasis, Instituto de Salud Carlos III, FEDER, Fundación Séneca.

Venous valve hypoxia as a possible mechanism of deep vein thrombosis: a scoping review

INTRODUCTION

The pathogenesis of deep vein thrombosis (DVT) has been explained by an interplay between a changed blood composition, vein wall alteration, and blood flow abnormalities. A comprehensive investigation of these components of DVT pathogenesis has substantially promoted our understanding of thrombogenesis in the venous system. Meanwhile, the process of DVT initiation remains obscure. This systematic review aims to collect, analyze, and synthesize the published evidence to propose hypoxia as a possible trigger of DVT.

EVIDENCE ACQUISITION

An exhaustive literature search was conducted across multiple electronic databased including PubMed, EMBASE, Scopus, and Web of Science to identify studies pertinent to the research hypothesis. The search was aimed at exploring the connection between hypoxia, reoxygenation, and the initiation of deep vein thrombosis (DVT). The following key words were used: "deep vein thrombosis," "venous thrombosis," "venous thromboembolism," "hypoxia," "reoxygenation," "venous valve," and "venous endothelium." Reviews, case reports, editorials, and letters were excluded.

EVIDENCE SYNTHESIS

Based on the systematic search outcome, 156 original papers relevant to the issue were selected for detailed review. These studies encompassed a range of experimental and observational clinical research, focusing on various aspects of DVT, including the anatomical, physiological, and cellular bases of the disease. A number of studies suggested limitations in the traditional understanding of Virchow's triad as an acceptable explanation for DVT initiation. Emerging evidence points to more complex interactions and additional factors that may be critical in the early stages of thrombogenesis. The role of venous valves has been recognized but remains underappreciated, with several studies indicating that these sites may act as primary loci for thrombus formation. A collection of studies describes the effects of hypoxia on venous endothelial cells at the cellular and molecular levels. Hypoxia influences several pathways that regulate endothelial cell permeability, inflammatory response, and procoagulation activity, underpinning the endothelial dysfunction noted in DVT.

CONCLUSIONS

Hypoxia of the venous valve may serve as an independent hypothesis to outline the DVT triggering process. Further research projects in this field may discover new molecular pathways responsible for the disease and suggest new therapeutic targets.

Activated protein C resistance in the copresence of emicizumab and activated prothrombin complex concentrates

Background

Venous thromboembolic events have been reported in persons with hemophilia A who received emicizumab and activated prothrombin complex concentrate (APCC) concomitantly, but the relevant mechanism(s) remains unclear. We speculated that activated protein C (APC) and antithrombin (AT) resistance might be associated with these adverse events.

Objectives

To investigate APC and AT resistance in factor (F)VIII-deficient (FVIIIdef) plasma in the presence of emicizumab and APCC.

Methods

In pooled normal plasma or FVIIIdef plasma samples mixed with emicizumab (50 μg/mL) and FVIII-bypassing agents, including recombinant FVIIa (2.2 μg/mL), APCC (1.3 IU/mL), or plasma-derived FVIIa/FX (1.5 μg/mL), the suppression effect of AT (0-2.4 μM) and APC (0-16 nM) was assessed by tissue factor-triggered thrombin generation assay. The APC effects in FVIIIdef plasma with the copresence of emicizumab, FII (1.3 μM), and/or FIXa (280 pM) were also examined.

Results

The AT resistance in emicizumab and each bypassing agent was not observed. Moreover, APC dose-dependent suppression effect was observed in pooled normal plasma or FVIIIdef plasma mixed with emicizumab and recombinant FVIIa or plasma-derived FVIIa/FX. However, APC-catalyzed inactivation had little effect on thrombin generation assay potential in FVIIIdef plasma spiked with emicizumab and APCC. The addition of FIXa to emicizumab in FVIIIdef plasma could lead to partial APC resistance. Furthermore, FVIIIdef plasma spiked with emicizumab, FIXa, and FII was markedly resistant to APC-mediated inactivation.

Conclusion

FII and FIXa in APCCs were key clotting factors for APC resistance in FVIIIdef plasma supplemented with emicizumab and APCCs. The APC resistance in persons with hemophilia A receiving emicizumab and APCC may contribute to venous thromboembolic events.

The dos, don'ts, and nuances of thrombophilia testing

Considerable progress has been made in elucidating genetic and biologic risk factors for venous thromboembolism (VTE). Despite being able to identify heritable defects in a substantial proportion of patients with VTE, testing has not, in general, proven useful in management. Despite efforts to reduce inappropriate testing, it often falls to the hematologist to consult on patients having undergone thrombophilia testing. Through a series of cases, we discuss how D-dimer testing can be helpful in VTE recurrence risk stratification in younger women as well as how to approach patients with persistently elevated D-dimer levels in the absence of thrombosis. While elevated factor VIII coagulant activity levels are a significant risk factor for a first episode of VTE, its biologic basis is not fully understood, and studies have not shown it to be a useful predictor of recurrence. Abnormal results of genetic tests for methylene tetrahydrofolate reductase or plasminogen activator 1 promoter polymorphisms may be encountered, which carry little if any thrombotic risk and should never be ordered. We also discuss protein S deficiency, the most difficult of the hereditary thrombophilias to diagnose due to a wider "normal" range in the general population as compared with protein C, the presence of both free and bound forms in plasma, and the characteristics of the various assays in use. We also present a rare type of protein C deficiency that can be missed by functional assays using an amidolytic rather than a clotting end point.

Laboratory Evaluation of Antithrombin, Protein C, and Protein S

Thrombophilia is a complex disease process, clinically manifesting in various forms of venous thromboembolism. Although both genetic and acquired (or environmental) risks factors have been reported, the presence of a genetic defect (antithrombin [AT], protein C [PC], protein S [PS]) is considered three of the major contributing factors of thrombophilia. The presence of each of these risk factors can be established by clinical laboratory analysis; however, the clinical provider and laboratory personnel must understand the testing limitations and shortcomings associated with the assays for these factors to be able to ensure an accurate diagnosis. This article will describe the major pre-analytical, analytical, and post-analytical issues associated with the various types of assays and discuss evidence-based algorithms for analyzing AT, PC, and PS in plasma.

Antithrombin lowering in hemophilia: a closer look at fitusiran

Thrombin is a key enzyme in the maintenance of normal hemostatic function and is the central product of an interconnected set of simultaneously occurring cellular and proteolytic events. Antithrombin (AT) is a natural anticoagulant that downregulates different components of the clotting process, particularly thrombin generation. In good health, well-regulated hemostasis is the result of a balance between procoagulant and anticoagulant elements. Cumulative understanding of the regulation of thrombin generation and its central role in hemostasis and bleeding disorders has led to the clinical development of therapeutic strategies that aim to rebalance hemostasis in individuals with hemophilia and other coagulation factor deficiencies to improve bleeding phenotype. The aim of this review is to discuss the rationale for AT lowering in individuals with hemophilia, with a focus on fitusiran, its mechanism of action, and its potential as a prophylactic therapy for individuals with hemophilia A or B, with or without inhibitors. Fitusiran is an investigational small, interfering RNA therapeutic that targets and lowers AT. It is currently in phase III clinical trials and results have shown its potential to increase thrombin generation, leading to enhanced hemostasis and improved quality of life while reducing the overall treatment burden.

Antithrombin Therapy: Current State and Future Outlook

Antithrombin (AT) is a natural anticoagulant pivotal in inactivating serine protease enzymes in the coagulation cascade, making it a potent inhibitor of blood clot formation. AT also possesses anti-inflammatory properties by influencing anticoagulation and directly interacting with endothelial cells. Hereditary AT deficiency is one of the most severe inherited thrombophilias, with up to 85% lifetime risk of venous thromboembolism. Acquired AT deficiency arises during heparin therapy or states of hypercoagulability like sepsis and premature infancy. Optimization of AT levels in individuals with AT deficiency is an important treatment consideration, particularly during high-risk situations such as surgery, trauma, pregnancy, and postpartum. Here, we integrate the existing evidence surrounding the approved uses of AT therapy, as well as potential additional patient populations where AT therapy has been considered by the medical community, including any available consensus statements and guidelines. We also describe current knowledge regarding cost-effectiveness of AT concentrate in different contexts. Future work should seek to identify specific patient populations for whom targeted AT therapy is likely to provide the strongest clinical benefit.

Laboratory Evaluation of Thrombophilia

Venous thromboembolism (VTE) occurs typically in the veins of the lower extremities and/or as pulmonary embolism. There is a myriad of causes of VTE ranging from provoked causes (e.g., surgery, cancer) to unprovoked causes (e.g., inherited abnormalities) or multiple factors that combine to initiate the cause. Thrombophilia is a complex, multi-factorial disease that may result in VTE. The mechanism(s) and causes of thrombophilia are complex and not completely understood. In healthcare today, only some answers about the pathophysiology, diagnosis, and prevention of thrombophilia have been elucidated. The laboratory analysis for thrombophilia is not consistently applied, and has changed over time, but remains varied by providers and laboratories as well. Both groups must establish harmonized guidelines for patient selection and appropriate conditions for analysis of inherited and acquired risk factors. This chapter discusses the pathophysiology of thrombophilia, and evidence-based medicine guidelines discuss the optimum laboratory testing algorithms and protocols for selection and analyzing VTE patients to ensure a cost-effective use of limited resources.

RNAi for the Treatment of People with Hemophilia: Current Evidence and Patient Selection

Severe hemophilia is associated with spontaneous, prolonged and recurrent bleeding. Inadequate prevention and treatment of bleeding can lead to serious morbidity and mortality. Due to the limitations of intravenous clotting factor replacement, including the risk of inhibitory antibodies, innovative novel therapies have been developed that have dramatically changed the landscape of hemophilia therapy. Ribonucleic acid interference (RNAi) has brought the opportunity for multiple strategies to manipulate the hemostatic system and ameliorate the bleeding phenotype in severe bleeding disorders. Fitusiran is a RNAi therapeutic that inhibits the expression of the natural anticoagulant serpin antithrombin. Reduction in antithrombin is known to cause thrombosis if coagulation parameters are otherwise normal and can rebalance hemostasis in severe hemophilia. Reports from late stage clinical trials of fitusiran in hemophilia A and B participants, with and without inhibitory antibodies to exogenous clotting factor, have demonstrated efficacy in preventing bleeding events showing promise for a future "universal" prophylactic treatment of individuals with moderate-severe hemophilia.

Antithrombin Deficiency: Frequency in Patients with Thrombosis and Thrombophilic Families

PURPOSE

Antithrombin (AT) deficiency is a well-known inherited risk factor for venous thromboembolism (VTE). However, F V Leiden and F II20210a mutations have drawn much more attention in the recent years. Therefore, we have decided to analyze the frequency of antithrombin deficiency in different cohorts of patients and tried to formulate indications for its testing.

RESULTS

Antithrombin deficiency was found in 4% of patients with recurrent VTE ≤ 50 years of age with, in 1% of patients with splanchnic vein thrombosis and in 2% of cases associated with combined oral contraceptives (COC) use or pregnancy. In patients with central venous thrombosis, antithrombin deficiency was not found.

RECOMMENDATION

We consider antithrombin testing useful in patients with thrombosis occuring up to 45 years of age without any risk factors. Namely, females with VTE in pregnancy and puerperium should be tested as well as females with thrombosis on COC, if VTE occurred within the first year of their use.

CONCLUSION

In spite of degressive interest in thrombophilia work up, we still consider antithrombin testing useful in defined clinical situations.

Antithrombin Activity and Association with Risk of Thrombosis and Mortality in Patients with Cancer

Venous and arterial thromboembolism (VTE/ATE) are common complications in cancer patients. Antithrombin deficiency is a risk factor for thrombosis in the general population, but its connection to risk of cancer-associated thrombosis is unclear. We investigated the association of antithrombin activity levels with risk of cancer-associated VTE/ATE and all-cause mortality in an observational cohort study including patients with cancer, the Vienna Cancer and Thrombosis Study. In total, 1127 patients were included (45% female, median age: 62 years). Amongst these subjects, 110 (9.7%) patients were diagnosed with VTE, 32 (2.8%) with ATE, and 563 (49.9%) died. Antithrombin was not associated with a risk of VTE (subdistribution hazard ratio (SHR): 1.00 per 1% increase in antithrombin level; 95% CI: 0.99-1.01) or ATE (SHR: 1.00; 95% CI: 0.98-1.03). However, antithrombin showed a u-shaped association with the risk of all-cause death, i.e., patients with very low but also very high levels had poorer overall survival. In the subgroup of patients with brain tumors, higher antithrombin levels were associated with ATE risk (SHR: 1.02 per 1% increase; 95% CI: 1.00-1.04) and mortality (HR: 1.01 per 1% increase; 95% CI: 1.00-1.02). Both high and low antithrombin activity was associated with the risk of death. However, no association with cancer-associated VTE and ATE across all cancer types was found, with the exception of in brain tumors.

Thrombosis and anticoagulation: clinical issues of special importance to hematologists who practice in Asia

There are clinical issues of special importance and practice variation in the management of venous thromboembolism (VTE) and in the use of anticoagulants among hematologists who practice in Asia. In Asian-inherited thrombophilia, coagulation is disturbed due to loss-of-function mutations of protein S and protein C causing protein S and protein C deficiencies, whereas the gain-of-function factor V Leiden and prothrombin G20210A mutations are almost absent. Thrombophilia screening is not recommended in patients with VTE patients who have major provoking factors. However, it can be considered in unprovoked young patients with VTE who have a strong family history of VTE. Cancer is the most important acquired risk factor for VTE in Asians. Limited cancer screening at the initial presentation of unprovoked VTE is appropriate, especially in the elderly. Direct oral anticoagulants have been shown to have similar efficacy and reduce risk of major bleeding, including intracranial hemorrhage and bleeding requiring hospitalization, compared with warfarin. Most clinical trials evaluating therapies for treatment and prevention of VTE have included small numbers of Asian patients. Despite this lack of evidence, direct oral anticoagulants have been increasingly used in Asia for cancer-associated thrombosis. Individualized assessment of thrombotic and bleeding risks should be used for all hospitalized Asian patients when deciding on pharmacologic thromboprophylaxis. More research is needed to understand the factors that contribute to risks of VTE and anticoagulant-associated bleeding in Asian patients as these may differ from Western populations.

Gene editing of human iPSCs rescues thrombophilia in hereditary antithrombin deficiency in mice

Hereditary antithrombin deficiency is caused by SERPINC1 gene mutations and predisposes to recurrent venous thromboembolism that can be life-threatening. Therefore, lifelong anticoagulation is required, which has side effects and may not be effective. In this study, peripheral blood mononuclear cells from a patient with severe antithrombin deficiency were reprogrammed into induced pluripotent stem cells (iPSCs). The mutation was corrected using CRISPR-Cas9 and Cre/LoxP genome editing. iPSCs were differentiated into hepatocytes, which were injected into the spleen of antithrombin knockout mice to restore the activity of antithrombin and reduce the thrombophilic state. Human iPSC-differentiated hepatocytes colonized mice and secreted antithrombin stably, normalizing antithrombin in plasma (activity: from 46.8 ± 5.7% to 88.6 ± 7.6%, P < 0.0001; antigen: from 146.9 ± 19.5 nanograms per milliliter to 390.7 ± 16.1 nanograms per milliliter, P < 0.0001). In venous thrombosis model, the rate of thrombosis in mice treated with edited hepatocytes, parental hepatocytes, and wild-type mice were 60, 90, and 70%, respectively. The thrombus weight was much lighter in mice treated with edited hepatocytes compared with parental hepatocytes (7.25 ± 2.00 milligrams versus 15.32 ± 2.87 milligrams, P = 0.0025) and showed no notable difference compared with that in wild-type mice (10.41 ± 2.91 milligrams). The activity and concentration of antithrombin remained high for 3 weeks after injection. The liver and kidney function markers showed no obvious abnormality during the observation period. This study provides a proof of principle for correction of mutations in patient-derived iPSCs and potential therapeutic applications for hereditary thrombophilia.

Full-length antithrombin frameshift variant with aberrant C-terminus causes endoplasmic reticulum retention with a dominant-negative effect

Antithrombin, a major endogenous anticoagulant, is a serine protease inhibitor (serpin). We characterized the biological and clinical impact of variants involving C-terminal antithrombin. We performed comprehensive molecular, cellular, and clinical characterization of patients with C-terminal antithrombin variants from a cohort of 444 unrelated individuals with confirmed antithrombin deficiency. We identified 17 patients carrying 12 C-terminal variants, 5 of whom had the p.Arg445Serfs*17 deletion. Five missense variants caused qualitative deficiency, and 7, including 4 insertion-deletion variants, induced severe quantitative deficiency, particularly p.Arg445Serfs*17 (antithrombin <40%). This +1 frameshift variant had a molecular size similar to that of WT antithrombin but possessed a different C-terminus. Morphologic and cotransfection experiments showed that recombinant p.Arg445Serfs*17 was retained at the endoplasmic reticulum and had a dominant-negative effect on WT antithrombin. Characterization of different 1+ frameshift, aberrant C-terminal variants revealed that protein secretion was determined by frameshift site. The introduction of Pro441 in the aberrant C-terminus, shared by 5 efficiently secreted variants, partially rescued p.Arg445Serfs*17 secretion. C-terminal antithrombin mutants have notable heterogeneity, related to variant type and localization. Aberrant C-terminal variants caused by 1+ frameshift, with similar size as WT antithrombin, may be secreted or not, depending on frameshift site. The severe clinical phenotypes of these genetic changes are consistent with their dominant-negative effects.

Gerinnungsdiagnostik im klinischen Alltag – Teil 2

Während bei einer Vitamin-K-Antagonisten-Therapie die Therapieüberwachung (International Normalized Ratio [INR]) obligat ist, gilt dies für direkte orale Antikoagulanzien (DOAK) oder niedermolekulares Heparin (NMH) nur in ausgewählten klinischen Szenarien. Bei DOAK steht die Bestimmung von Tal- und Spitzenspiegeln des Medikaments im Plasma im Vordergrund, bei NMH die Anti-Xa-Aktivität. Der Zeitpunkt der Probenabnahme in Relation zur Einnahme ist für die Bewertung essenziell. Eine neu aufgetretene Thrombozytopenie im Rahmen stationärer Behandlungen ist häufig. Einordnung der Grunderkrankung, Tag des Auftretens sowie Erfassung medikamentöser Einflüsse und ihrer Dynamik ermöglichen oft die Eingrenzung der Ursache. Die Thrombophilietestung nach venöser Thromboembolie wird aufgrund fehlender therapeutischer Konsequenz zunehmend seltener durchgeführt. Ein Antiphospholipidsyndrom darf aber nicht übersehen werden, da sowohl die Therapiedauer als auch die Wahl des Antikoagulans davon abhängen.

Long-Read Sequencing Identifies the First Retrotransposon Insertion and Resolves Structural Variants Causing Antithrombin Deficiency

The identification of inherited antithrombin deficiency (ATD) is critical to prevent potentially life-threatening thrombotic events. Causal variants in SERPINC1 are identified for up to 70% of cases, the majority being single-nucleotide variants and indels. The detection and characterization of structural variants (SVs) in ATD remain challenging due to the high number of repetitive elements in SERPINC1. Here, we performed long-read whole-genome sequencing on 10 familial and 9 singleton cases with type I ATD proven by functional and antigen assays, who were selected from a cohort of 340 patients with this rare disorder because genetic analyses were either negative, ambiguous, or not fully characterized. We developed an analysis workflow to identify disease-associated SVs. This approach resolved, independently of its size or type, all eight SVs detected by multiple ligation-dependent probe amplification, and identified for the first time a complex rearrangement previously misclassified as a deletion. Remarkably, we identified the mechanism explaining ATD in 2 out of 11 cases with previous unknown defect: the insertion of a novel 2.4 kb SINE-VNTR-Alu retroelement, which was characterized by de novo assembly and verified by specific polymerase chain reaction amplification and sequencing in the probands and affected relatives. The nucleotide-level resolution achieved for all SVs allowed breakpoint analysis, which revealed repetitive elements and microhomologies supporting a common replication-based mechanism for all the SVs. Our study underscores the utility of long-read sequencing technology as a complementary method to identify, characterize, and unveil the molecular mechanism of disease-causing SVs involved in ATD, and enlarges the catalogue of genetic disorders caused by retrotransposon insertions.

Prevalence of venous thromboembolism and its associations in a large racially homogenous population of sickle cell disease patients

To determine the prevalence of venous thromboembolism (VTE) among adult sickle cell disease (SCD) patients in Nigeria.

METHODS

This was a multicentre retrospective study in which the medical records of adult SCD patients were reviewed. Information on demographics, steady-state haemogram, clinical phenotypes, duration of follow-up, history of VTE including risk factors and management was collected.

RESULTS

Of the 509 SCD patients with a median (IQR) duration of follow-up of 2 years, 10 (2.0%) had VTE (9 DVT and 1 PE). Their median (IQR) age was 27 (22.8-30.3) years. Identifiable risk factors for VTE included positive family history (2, 20%) surgery, splenectomy, paraplegia and cancer (1, 10% each). No risk factor was identifiable in four persons. VTE had no significant association with age and gender. VTE was significantly associated with the following events: acute chest syndrome [p = .002, odds ratio (OR) 8, 95% CI 2.2-28.9], osteonecrosis [p = .012, OR 5.24, 95% CI, 1.45-18.91] and vaso-occlusive crisis [p = .035]. Also significantly associated with VTE were pulmonary hypertension [p = .001, OR 23.3, 95%CI 5.18-105.06] and stroke [p = .032, OR 9.35, 95%CI 0.87-53.25].

CONCLUSION

The prevalence of VTE among SCD patients in Nigeria is low. It is significantly associated with vaso-occlusive crisis, pulmonary hypertension and stroke.

Inherited thrombophilia transpires with severe coronary arterial thrombosis in wide range of age backgrounds: A report of 3 cases

Introduction

and importance: Protein C and S deficiency are some of the coagulation cascade disorders which may also contributes not only to venous thromboembolism (VTE), but also rarely to arterial thrombosis. Here we present a report of 3 severe coronary artery disease (CAD) cases ranging from very young to elderly patients with concomitant inherited thrombophilia.

Case presentation

The first case was a chronic coronary syndrome from a very young male patient with history of VTE without any other risk factor of CAD. The second case was about premature CAD with triple chronic total occlusion (RCA, LCX, LAD) in patient under 45 years old, with single risk factor. The third case was about accelerated atherosclerosis progression from previously non significant stenosis in RCA into total occlusion in RCA and inferior STEMI in old patient on supposely adequate double anti platelet agent.

Clinical discussion

All patients had protein C and/or S deficiency and first degree family history of VTE, therefore inherited thrombophilia was diagnosed. We gave them oral anticoagulant in addition to their standard treatment for secondary prevention with good outcome and without further adverse event.

Conclusion

It is important to raise awareness to perform screening inherited thrombophilia as an important risk factor for CAD in special subgroup such as young age patient with rapid course progression and family history of VTE. The use of oral anticoagulants as either prophylactic or therapeutic purpose in patients with inherited thrombophilia are safe and effective. However, further research is still needed.

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Inherited thrombophilia is a rare disease that can causes coronary arterial thrombosis.

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Inherited thrombophilia screening should be done in special subgroup of patients.

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There is no treatment guideline for CAD patients with inherited thrombophilia.

Approach to Thrombophilia in Pregnancy-A Narrative Review

Thrombophilia is a genetic predisposition to hypercoagulable states caused by acquired haemostasis conditions; pregnancy causes the haemostatic system to become hypercoagulable, which grows throughout the pregnancy and peaks around delivery. Genetic testing for thrombophilic gene mutations is evaluated using different methodologies of real-time polymerase chain reaction and DNA microarrays of specific genes. Adapting the general care of the pregnant woman to the particularities caused by thrombophilia is an important component, so screening is preferred to assess the degree of genetic damage that manifests itself as a risk of thrombosis. The major goal of this narrative review was to quantitatively evaluate the literature data on the specific care of pregnant women with thrombophilia that are at risk of developing unplanned miscarriages.

Two SERPINC1 variants affecting N-glycosylation of Asn224 cause severe thrombophilia not detected by functional assays

Antithrombin deficiency, the most severe congenital thrombophilia, might be underestimated, as some pathogenic variants are not detected by routine functional methods. We have identified two new SERPINC1 variants, p.Glu227Lys and p.Asn224His, in four unrelated thrombophilic patients with early and recurrent thrombosis that had normal antithrombin activity. In one case, the mutation was identified by whole genome sequencing, while in the 3 remaining cases, the mutation was identified by sequencing SERPINC1 based on a single functional positive finding supporting deficiency. The two variants shared a common functional defect, an impaired or null N-glycosylation of Asn224 according to a eukaryotic expression model. Carriers had normal anti-FXa or anti-FIIa activities, but impaired anti-FVIIa activity and a detectable loss of inhibitory function when incubating the plasma 1 hour at 41ºC. Moreover, the beta glycoform of the variants, lacking two N-glycans, had reduced secretion, increased heparin affinity, no inhibitory activity, and a potential dominant negative effect. These results explain the increased thrombin generation observed in carriers. Mutation experiments reflected the role that Lysine residues close to the N-glycosylation sequon have in impairing the efficacy of N-glycosylation. Our study shows new elements involved in the regulation of N-glycosylation, a key post-translational modification that, according to our results affects folding, secretion and function, providing new evidence of the pathogenic consequence of an incorrect N-glycosylation of antithrombin. This study supports that antithrombin deficiency is underestimated and encourages the development of new functional and genetic tests to diagnose this severe thrombophilia.

Molecular and clinical characterization of transient antithrombin deficiency: A new concept in congenital thrombophilia

Antithrombin deficiency, the most severe thrombophilia, might be underestimated, since it is only investigated in cases with consistent functional deficiency or family history. We have analyzed 444 consecutive, unrelated cases, from 1998 to 2021, with functional results supporting antithrombin deficiency in at least one sample. Plasma antithrombin was evaluated by functional and biochemical methods in at least two samples. SERPINC1 gene was analyzed by sequencing and MPLA. Hypoglycosylation was studied by electrophoresis and high-performance liquid chromatography (HPLC). In 260 of 305 cases (85.2%) with constitutive deficiency (activity < 80% in all samples), a SERPINC1 (N = 250), or N-glycosylation defect (N = 10) was observed, while 45 remained undetermined. The other 139 cases had normal antithrombin activity (≥ 80%) in at least one sample, what we called transient deficiency. Sixty-one of these cases (43.9%) had molecular defects: 48 had SERPINC1 variants, with two recurrent mutations (p.Ala416Ser[Cambridge II], N = 15; p.Val30Glu[Dublin], N = 12), and 13 hypoglycosylation. Thrombotic complications occurred in transient deficiency, but were less frequent, latter-onset, and had a higher proportion of arterial events than in constitutive deficiency. Two mechanisms explained transient deficiency: The limitation of functional methods to detect some variants and the influence of external factors on the pathogenic consequences of these mutations. Our study reveals a molecular defect in a significant proportion of cases with transient antithrombin deficiency, and changes the paradigm of thrombophilia, as the pathogenic effect of some mutations might depend on external factors and be present only at certain timepoints. Antithrombin deficiency is underestimated, and molecular screening might be appropriate in cases with fluctuating laboratory findings.

Cost-Effective Use of the Protein S Algorithm in Thrombophilia Testing

Background

One of the most complex risk factors for the laboratory assessment of thrombophilia is Protein S (PS). The testing algorithm for PS employs the plasma-based assays of free PS antigen, total PS antigen, and PS activity creating a complex diagnostic scheme that can lead to misdiagnosis if incorrectly used, and a potential waste of resources and money.

Content

This paper compares the recently published evidence-based algorithm from the International Society for Hemostasis and Thrombosis (ISTH) with several commonly performed nonevidence-based testing schemes, to demonstrate the efficiency of the evidence-based algorithm for diagnostic efficiency with improved patient care and increased cost savings for the laboratory.

Summary

Significant savings (31%–60%) can be realized when the evidence-based algorithm is used in place of other testing modalities of initial PS activity testing (31%) or testing with all 3 assays simultaneously (60%). This study utilizing the PS testing evidence-based algorithm as part of a thrombophilia evaluation demonstrates that the appropriate testing methods can be used to limit wasteful practices while achieving the maximum level of information in this time of limited resources and need for increase monetary savings.

Predicting risk factors for thromboembolic complications in patients with sickle cell anaemia - lessons learned for prophylaxis

Objective

To assess the clinical and laboratory predictors of venous thromboembolism (VTE) in patients with sickle cell anaemia (SCA) and its relationship to morbidity and mortality.

Methods

This retrospective case–control study analysed data from patients with SCA that experienced VTE compared with matched control patients with SCA but no VTE (2:1 ratio).

Results

A total of 102 patients with SCA were enrolled (68 cases with VTE and 34 controls). Amongst the 68 cases (median age, 29.5 years), 26 (38.2%) presented with isolated pulmonary embolism (PE). A higher prevalence of splenectomy (73.5% versus 35.3%) was observed in the cases compared with the controls. A significantly higher prevalence of central venous catheter (CVC) insertion (42.6% versus 8.8%) was observed in the cases compared with the controls. High white blood cell counts, serum lactic dehydrogenase (LDH), bilirubin and C-reactive protein (CRP) and low haemoglobin (Hb) and HbF were significant risk factors for VTE. Forty-two cases (61.8%) developed acute chest syndrome, 10 (14.7%) had a stroke and seven (10.3%) died.

Conclusions

VTE in patients with SCA has a high impact on morbidity and mortality. PE was the leading presentation of VTE, with CVC insertion, high LDH, bilirubin, CRP and white blood cell counts along with low Hb and HbF constituting other significant risk factors.

Downregulation of microRNA-200c-3p alleviates the aggravation of venous thromboembolism by targeting serpin family C member 1

Venous thromboembolism (VTE) is the third most prevalent cardiovascular complication. Increasing studies have demonstrated that some microRNAs (miRNAs) are aberrantly expressed in VTE and play crucial roles in mediating the development of VTE. Therefore, our study intends to explore the detailed function and molecular mechanism of miR-200c-3p in VTE progression. In our research, VTE rat models were first established via inferior vena cava (IVC) ligation and the time-dependent effects of IVC ligation on thrombus formation were discovered. The results of reverse transcription quantitative polymerase-chain reaction (RT-qPCR) and western blotting showed that serpin family C member 1 (SERPINC1) was downregulated in VTE rat models and showed an inverse correlation with thrombus load. MiRNA target prediction tools and luciferase reporter assay confirmed SERPINC1 as a target for miR-200c-3p. VTE rats were injected with miR-200c-3p inhibitor for 24 h to investigate whether miR-200c-3p knockdown influences thrombus formation in vivo. Histological examination through hematoxylin-eosin staining revealed that miR-200c-3p downregulation markedly inhibited the formation of thrombus in IVC of rats. Additionally, miR-200c-3p was upregulated while SERPINC1 was downregulated in serum and inferior vena cava of VTE rats as well as in plasma of patients with VTE. Linear regression analysis demonstrated that miR-200c-3p expression was negatively correlated to SERPINC1 expression in VTE rats and patients with VTE. Our study determines the previously unelucidated function of miR-200c-3p in VTE, which might provide a potential novel insight for the treatment of VTE.

An artificial neural network approach integrating plasma proteomics and genetic data identifies PLXNA4 as a new susceptibility locus for pulmonary embolism

Venous thromboembolism is the third common cardiovascular disease and is composed of two entities, deep vein thrombosis (DVT) and its potential fatal form, pulmonary embolism (PE). While PE is observed in ~ 40% of patients with documented DVT, there is limited biomarkers that can help identifying patients at high PE risk. To fill this need, we implemented a two hidden-layers artificial neural networks (ANN) on 376 antibodies and 19 biological traits measured in the plasma of 1388 DVT patients, with or without PE, of the MARTHA study. We used the LIME algorithm to obtain a linear approximate of the resulting ANN prediction model. As MARTHA patients were typed for genotyping DNA arrays, a genome wide association study (GWAS) was conducted on the LIME estimate. Detected single nucleotide polymorphisms (SNPs) were tested for association with PE risk in MARTHA. Main findings were replicated in the EOVT study composed of 143 PE patients and 196 DVT only patients. The derived ANN model for PE achieved an accuracy of 0.89 and 0.79 in our training and testing sets, respectively. A GWAS on the LIME approximate identified a strong statistical association peak (rs1424597: p = 5.3 × 10^-7) at the PLXNA4 locus. Homozygote carriers for the rs1424597-A allele were then more frequently observed in PE than in DVT patients from the MARTHA (2% vs. 0.4%, p = 0.005) and the EOVT (3% vs. 0%, p = 0.013) studies. In a sample of 112 COVID-19 patients known to have endotheliopathy leading to acute lung injury and an increased risk of PE, decreased PLXNA4 levels were associated (p = 0.025) with worsened respiratory function. Using an original integrated proteomics and genetics strategy, we identified PLXNA4 as a new susceptibility gene for PE whose exact role now needs to be further elucidated.

Venous Thromboembolism: Genetics and Thrombophilias

Venous thromboembolism (VTE) is a major cause of morbidity and mortality throughout the world. Up to one half of patients who present with VTE will have an underlying thrombophilic defect. This knowledge has led to a widespread practice of testing for such defects in patients who develop VTE. However, identifying a hereditary thrombophilia by itself does not necessarily change outcomes or dictate therapy. Furthermore, family history of VTE by itself can increase an asymptomatic person's VTE risk several-fold, independent of detecting a known inherited thrombophilia. In this article, we will describe the current validated hereditary thrombophilias including their history, prevalence, and association with VTE. With a focus on evaluating both risks and benefits of testing, we will also explore the controversies of why, who, and when to test as well as discuss contemporary societal guidelines. Lastly, we will share how these tests have been integrated into clinical practice and how to best utilize them in the future.

Platelet protein S limits venous but not arterial thrombosis propensity by controlling coagulation in the thrombus

Anticoagulant protein S (PS) in platelets (PSplt) resembles plasma PS and is released on platelet activation, but its role in thrombosis has not been elucidated. Here we report that inactivation of PSplt expression using the Platelet factor 4 (Pf4)-Cre transgene (Pros1lox/loxPf4-Cre+) in mice promotes thrombus propensity in the vena cava, where shear rates are low, but not in the carotid artery, where shear rates are high. At a low shear rate, PSplt functions as a cofactor for both activated protein C and tissue factor pathway inhibitor, thereby limiting factor X activation and thrombin generation within the growing thrombus and ensuring that highly activated platelets and fibrin remain localized at the injury site. In the presence of high thrombin concentrations, clots from Pros1lox/loxPf4-Cre- mice contract, but not clots from Pros1lox/loxPf4-Cre+ mice, because of highly dense fibrin networks. Thus, PSplt controls platelet activation as well as coagulation in thrombi in large veins, but not in large arteries.

N-Glycosylation as a Tool to Study Antithrombin Secretion, Conformation, and Function

N-linked glycosylation is a crucial post-translational modification involved in protein folding, function, and clearance. N-linked glycosylation is also used therapeutically to enhance the half-lives of many proteins. Antithrombin, a serpin with four potential N-glycosylation sites, plays a pivotal role in hemostasis, wherein its deficiency significantly increases thrombotic risk. In this study, we used the introduction of N-glycosylation sites as a tool to explore what effect this glycosylation has on the protein folding, secretion, and function of this key anticoagulant. To accomplish this task, we introduced an additional N-glycosylation sequence in each strand. Interestingly, all regions that likely fold rapidly or were surrounded by lysines were not glycosylated even though an N-glycosylation sequon was present. The new sequon in the strands of the A- and B-sheets reduced secretion, and the B-sheet was more sensitive to these changes. However, the mutations in the strands of the C-sheet allowed correct folding and secretion, which resulted in functional variants. Therefore, our study revealed crucial regions for antithrombin secretion and could potentially apply to all serpins. These results could also help us understand the functional effects of natural variants causing type-I deficiencies.

Recommendations for clinical laboratory testing for protein S deficiency: Communication from the SSC committee plasma coagulation inhibitors of the ISTH

Hereditary deficiencies of protein S (PS) increase the risk of venous thrombosis; however, assessing the plasma levels of PS can be difficult because of its complex physiological interactions in plasma, sample-related preanalytical variables, and numerous acquired disease processes. Reliable laboratory assays are essential for accurate evaluation of PS when diagnosing a congenital deficiency based on the plasma phenotype alone. This report presents the current evidence-based recommendations for clinical PS assays as well as when to test for PS abnormalities.

Patent Foramen Ovale Attributable Cryptogenic Embolism With Thrombophilia Has Higher Risk for Recurrence and Responds to Closure

OBJECTIVES

The aim of this study was to investigate the effect of management on the risk for recurrent events among patients with cryptogenic ischemic stroke or transient ischemic attack.

BACKGROUND

The combination of patent foramen ovale (PFO) and hypercoagulability may greatly increase the risk for paradoxical embolism. However, previous randomized controlled trials evaluating the efficacy of PFO closure excluded these potential high-risk patients.

METHODS

Patients diagnosed with PFO attributable cryptogenic embolism were prospectively, without randomization, recruited from January 2005 to March 2018. The relationship between thrombophilia and recurrent events was evaluated in overall patients. Multivariate Cox regression was conducted to assess the relative risk for recurrence in PFO closure and medical therapy groups.

RESULTS

A total of 591 patients with cryptogenic embolism with PFO were identified. The median duration of follow-up was 53 months, and thrombophilia significantly increased the risk for recurrent events (hazard ratio [HR]: 1.85; 95% confidence interval [CI]: 1.09 to 3.16; p = 0.024). PFO closure was superior to medical therapy in overall patients (HR: 0.16; 95% CI: 0.09 to 0.30; p < 0.001). Of the 134 patients (22.7%) with thrombophilia, there was a difference in the risk for recurrence events between the PFO closure (6 of 89) and medical therapy (15 of 45) groups (HR: 0.25; 95% CI: 0.08 to 0.74; p = 0.012). There was no potential heterogeneity in the further subgroup analysis.

CONCLUSIONS

Patients with cryptogenic stroke with PFO and hypercoagulable state had increased risk for recurrent stroke or transient ischemic attack. PFO closure provided a lower risk for recurrent events compared with medical therapy alone.

Direct Oral Anticoagulants in Patients With Inherited Thrombophilia and Venous Thromboembolism: A Prospective Cohort Study

Background

In this prospective cohort study, we aimed to evaluate the efficacy and safety of direct oral anticoagulants (DOACs) versus heparin/vitamin K antagonists for the treatment of venous thromboembolism (VTE) in patients with inherited thrombophilia.

Methods and Results

We enrolled consecutive patients with acute VTE and inherited thrombophilia treated with DOACs (cases) or heparin/vitamin K antagonists (controls), matched for age, sex, ethnicity, and thrombophilia type. End points were VTE recurrence and bleeding complications; residual vein thrombosis and post‐thrombotic syndrome; VTE recurrence after anticoagulant discontinuation. Two hundred fifty‐five cases (age 52.4±17.3 years, Female 44.3%, severe thrombophilia 33.1%) and 322 controls (age 49.7±18.1 years, Female 50.3%, severe thrombophilia 35.1%) were included. The cumulative incidence of VTE recurrence during anticoagulation was 1.09% in cases versus 1.83%, adjusted hazard ratio (HR) 0.67 (95% CI, 0.16–2.77). The cumulative incidence of bleeding was 10.2% in cases versus 4.97%, HR 2.24 (95% CI 1.10–4.58). No major bleedings occurred in cases (versus 3 in controls). No significant differences regarding residual vein thrombosis and post‐thrombotic syndrome. After anticoagulant discontinuation, DOACs yielded a significantly lower 2‐year VTE recurrence risk versus traditional anticoagulants (HR, 0.61 [95% CI, 0.47–0.82]).

Conclusions

DOACs and heparin/vitamin K antagonists showed a similar efficacy in treating VTE in patients with thrombophilia. Although major bleeding episodes were recorded solely with heparin/vitamin K antagonists, we noted an overall increased bleeding rate with DOACs. The use of DOACs was associated with a lower 2‐year risk of VTE recurrence after anticoagulant discontinuation.

Frequency of thrombophilia associated genes variants: population-based study

BACKGROUND

Thrombophilia is a hypercoagulable state that may have a genetic basis (inherited) or can be acquired. It is a multifactorial condition and only the mutual interactions between the environment and genes may lead to the development of clinical manifestation. This state is the main factor promoting venous (rarely arterial) thromboembolism (VTE). Inherited thrombophilia is mainly associated with two pathogenic variants in the V coagulation factor (FV) and the prothrombin (FII) genes. The aim of our study was to evaluate the frequency of two pathogenic variants in FII and FV genes as inherited thrombophilia factors in a group within the Polish population in comparison with other described populations.

METHODS

All studied groups consisted of 633 unrelated patients aged between 18 and 70. Individuals in the research group come from the Podlasie region of Poland. Genotyping of FII and FV variants was performed using the 7900HT Fast Real-Time PCR System and were genotyped by TaqMan assay.

RESULTS

The pathogenic allele frequency for A allele was 0.03 (3%) and 0.07 (7%) for FII and FV genes, respectively. The GA/AA genotypes (c.*97G > A variant) were observed in only 33 (5.03%) individuals in the studied group. Additionally, the frequency of GA/AA genotypes was over 17.4% in the coagulation factor V. Co-incidence of heterozygous genotype GA of variants FII and FV genes was observed in only 4 subjects.

CONCLUSION

The FII gene variant shown in our study is less frequent than in other European countries (about 6%). In contrast, the A allele of the FV gene occurs with a frequency similar to that of Northern, Central and South Central Europe (about 5%).

Targeted gene expression analysis of human deep veins

OBJECTIVE

Endothelial-derived molecules involved in thrombosis and hemostasis have been investigated mainly in arteries and in experimental animals. The actual presence and integral function of these molecules in the human deep venous system have received less attention. Our aim was to evaluate the expression of certain prothrombotic and antithrombotic genes in the normal human deep veins of the lower extremities.

METHODS

Macroscopically intact and competent valve-containing segments of human deep veins were prospectively collected from patients who had undergone above-knee amputation. Vein samples were separated into four zones: zone 1, postvalve (downstream, proximal) vein wall; zone 2, the valve cusp; zone 3, prevalve (upstream, distal) vein wall; and zone 4, vein wall within the valve cusp (cusp removed). Real-time quantitative polymerase chain reaction for principal genes involved in coagulation, fibrinolysis, and inflammation was performed to quantify messenger RNA. Selected protein gene products were measured by the western blot assay. One additional valve-containing segment underwent mass spectrometry analysis to investigate global differences in the proteome between the study zones.

RESULTS

Seventeen valve-containing vein segments were analyzed. Significant upregulation of antithrombotic (protein C receptor [PROCR], thrombomodulin [THBD], tissue factor pathway inhibitor [TFPI]), prothrombotic (con Willebrand factor [VWF]), and proinflammatory (selectin P [SELP], intercellular adhesion molecule 1 [ICAM1]) genes was found in the valve cusp compared with the vein wall (P < .05). PROCR and THBD demonstrated the highest level of upregulation in the valve cusp. PROCR, serpin peptidase inhibitor, clade E, member 1 (SERPINE1), and SELP were upregulated in the valve cusp at the protein level (P < .05). Messenger RNA composition in the vein wall within the valve cusp was similar to the prevalve and postvalve vein wall for all genes, except for two times overexpressed ICAM1 (P < .05). Substantial differences within the proteome between the study zones were observed with mass spectrometry.

CONCLUSIONS

The biological properties of the valve cusp, vein wall within the valve cusp, and vein wall beyond the valve cusp are different. The endothelium of the valve cusps of a normal competent deep venous valve may be naturally less thrombogenic compared with the vein wall. The endothelium of the valve cusp may have a higher potential to interact with white blood cells compared with the vein wall. Mass spectrometry demonstrates substantial differences in the proteome between the vein wall and the valve cusps that were not anticipated before. (J Vasc Surg Venous Lymphat Disord 2021;9:770-80.) CLINICAL RELEVANCE: Deep vein thrombosis (DVT) is a major cause of mortality, morbidity, and impaired quality of life. Multiple risk factors have been identified, although their relative weight and pathophysiologic interactions remain obscure. Many patients with multiple risk factors for DVT never develop this condition. Conversely, in numerous cases DVT cannot be attributed to any known clinical risk factor. The molecular mechanisms that initiate DVT are unclear. An improved understanding of the normal biology of human deep veins will serve as an important foundation for new hypotheses of the pathogenesis of DVT. The latter may suggest new projects on novel therapeutic strategies.

Thrombophilia evaluation in pulmonary embolism

PURPOSE OF REVIEW

Patients with pulmonary embolism commonly undergo thrombophilia evaluation for a variety of reasons including risk stratification for recurrent venous thromboembolism (VTE) and treatment planning. However, the utility of thrombophilia testing in many clinical scenarios remains unclear. This review evaluates current recommendations for thrombophilia testing described in consensus VTE guidelines, recent literature on the clinical application of these recommendations, novel genetic assessments for hereditary thrombophilias, and studies evaluating use of direct oral anticoagulants (DOACs) in VTE patients with thrombophilias.

RECENT FINDINGS

Current VTE guidelines advise limited use of thrombophilia testing, recognizing that testing may be misinterpreted and frequently does not lead to a change in management. Testing and test results are not necessarily benign, are frequently misinterpreted, and can lead to increased anxiety in both patients and clinicians. Recent studies have offered innovative techniques to better align clinical practice with these recommendations as well as expanded genomic assessments to improve the scope and predictive value of thrombophilia testing. There is also emerging literature on the appropriateness of direct oral anticoagulant therapy for VTE patients with hereditary thrombophilias or antiphospholipid syndrome.

SUMMARY

Thrombophilia testing in its current form does not significantly impact clinical management or improve outcomes for most VTE patients. Therefore, it should be employed judiciously and only in patients for whom it is likely to alter clinical management. Novel expanded genomic thrombophilia testing approaches and additional studies evaluating optimal anticoagulant treatment in various thrombophilia subpopulations will make thrombophilia testing more useful for patients moving forward.

How I treat patients with hereditary antithrombin deficiency

Genetic predispositions to venous thromboembolism (VTE) are relatively frequent in the general population and comprise a heterogeneous group of disorders. Whereas the most frequent congenital risk factors for thrombosis only moderately increase the risk, a deficiency in antithrombin (AT), one of the most important natural inhibitors of blood coagulation, carries a higher risk. Congenital AT deficiency is an infrequently encountered genetic risk factor for VTE, and different subtypes vary with regard to their thrombotic risk. Patients with congenital AT deficiency, especially those with quantitative deficiency (type 1), may develop thrombosis early in life and often have a conspicuous family history of first- and second-degree relatives with VTE. Women are particularly affected because of the risk potentiation by combined estrogen/progestogen oral contraceptive use or pregnancy. The lack of controlled trials or even observational studies of large cohorts does not allow therapeutic decisions to be based on scientific evidence. In this review, we will discuss cases with thrombotic manifestations and the tailored management of patients with this congenital thrombosis risk factor.

Incidence of hereditary thrombophilia in patients with cranial dural arteriovenous fistulae

Dural arteriovenous fistulas (DAVFs) can develop as consequence of prior venous sinus thrombosis. However, the prevalence of prothrombotic conditions in patients with intracranial DAVFs is unknown and there is no consensus on the indications to screen for procoagulable conditions in these patients. We performed a retrospective review of patients presenting to our institution for management of cranial DAVF. Patient and DAVF characteristics were noted, in particular the incidence of hereditary thrombophilia (HT) detected by laboratory evaluation. Respective comparisons of patients with and without HT were performed using comparative statistics. There were 165 patients presenting for management of 171 DAVFs. A large proportion of DAVF were located at a large dural sinus (42.7%), which included superior sagittal, transverse, and sigmoid sinuses. On multivariate logistic regression analysis cortical venous drainage was independently associated with hemorrhagic presentation (OR 8.23, 95% CI 1.78-38.08; p = 0.007). A HT was detected in 18 of 61 patients (29.5%) who underwent a thrombophilia work-up. Location at a large dural sinus was not more common in patients with a HT (55.0% vs 54.5%; p = 0.97). There was also no difference in the presence of cortical venous drainage (56.5% vs 38.6%; p = 0.22) or hemorrhage on presentation (15.9% vs 5.0%; p = 0.22) in patients with and without a HT. In HT were found to be highly prevalent in our cohort, though our results do not suggest their presence greatly influences DAVF pathophysiology. Screening for procoagulable states is indicated in selected patients with an intracranial DAVF.

Diagnosis and management of congenital thrombophilia in the era of direct oral anticoagulants

Direct oral anticoagulants (DOAC)s are often preferred to other anticoagulants as they are more practical and do not require routine laboratory monitoring. Less is known about their use in congenital thrombophilia. Efficacy of DOACs in congenital thrombophilia, effect of DOACs and other anticoagulants on diagnostic tests as well as efficacy and safety of anticoagulant use in this population is still a matter of debate. In this review we intended to analyze the potential pitfalls of testing for thrombophilia in patients using DOACs and vitamin K antagonists (VKA)s as well as to suggest strategies to improve diagnostic accuracy in this setting. We also reviewed the literature for evidence regarding the safety and efficacy of DOACs in patients with congenital thrombophilia. Some evidence was found supporting the use of DOACs in low risk thrombophilia, although evidence for their use in high risk thrombophilia is limited to small series and case reports. Our findings support the generation of better evidence to support DOAC use for congenital thrombophilia, especially in the high risk subgroups.

Significance of a Family-based Study of Hereditary Thrombosis: A Single-family Case Series of Protein C Deficiency

Thrombophilia is a serious unpredictable complication caused by gene mutations, resulting in anticoagulant deficiencies. We herein report a single-family case series of protein C (PC) deficiency. Case 1 involved a Japanese man whose PC deficiency resulted in severe systemic thrombosis. The patients in cases 2 and 3 were his daughters who were diagnosed with PC deficiency via carrier screening in 2001 and later both became pregnant. Owing to appropriate treatments during pregnancy, they did not develop thrombosis and safely gave birth to healthy infants. This family case series suggests that appropriate knowledge concerning thrombophilia helps prevent future emergencies.

Direct Oral Anticoagulants in Patients Affected by Major Congenital Thrombophilia

Background

Thrombophilia is a condition that predisposes to a higher incidence of venous thromboembolisms (VTE), some also in atypical sites. Direct oral anticoagulants (DOACs) have proven to be effective in the treatment of deep vein thrombosis (DVT). However, their use can be sometimes challenging in particular settings of patients such as those with major thrombophilia - antithrombin, protein C and protein S deficiency, homozygous mutation of Factor V Leiden, homozygous mutation of Factor II G20210A, combined heterozygous mutation of factor V Leiden and Factor II G20210A - carrying a high thrombotic risk.

Patients and Methods

At our Center, 45 patients with major thrombophilia were treated with DOACs: 33 after an initial treatment with vitamin K antagonists (VKA) and 12 as first-line therapy for VTE. The median follow-up of DOACs treatment was 29 months.

Conclusions

No patient presented hemorrhagic or thrombotic complications during DOAC therapy. DOACs have proven to be effective and safe in this real-life series of patients with major thrombophilia.

Protein C and protein S deficiencies may be related to survival among hemodialysis patients

Background

Thrombophilia due to protein C (PC) and protein S (PS) deficiencies is highly prevalent among patients with stage 5 chronic kidney disease and is reported to arise due to extracorporeal circulation during hemodialysis (HD). This study aimed to evaluate the relationship between HD treatment and thrombophilia.

Methods

A total of 114 Japanese patients on maintenance HD (62 men, 52 women) were followed during 2008–2011. Their survival rates were compared against the duration of HD. Prior to each HD, coagulation/fibrinolysis parameters and PC and PS activities were measured using standard techniques. The patients were divided into two groups: Group 1, with PC and/or PS deficiencies (n = 32), and Group 2, without PC and PS deficiencies (n = 82). The influence of such deficiencies and duration of dialysis on survival was examined. Time-to-event analysis was applied using Kaplan-Meier estimates, and the log-rank test was proposed to test the equivalence of relative survival data. Hazard ratios and 95% confidence intervals (CI) were calculated.

Results

Of the 114 patients, 37 died (Group 1, 22; Group 2, 15). The hazard ratio (95% CI) was higher (p = 0.004) in Group 1 than Group 2. Gene analyses of PC and PS were performed in 14 patients from Group 1. No mutations in either protein were observed. We analyzed the causes of death in both groups; however, the estimated thrombophilia-related incidence of death could not be determined due to small sample size of HD patients.

Conclusions

Our results suggest that PC and PS deficiencies may be related to survival in HD patients. However, this finding warrants additional research.

Management of antithrombin deficiency: an update for clinicians

Introduction. Antithrombin is a serpin that inhibits multiple procoagulant serine proteases and acts as an endogenous anticoagulant. Thus, congenital antithrombin deficiency constitutes a major thrombophilic state, the most severe so far. Areas covered. In the present work, we globally review the biology, genetics, diagnosis, and management of congenital antithrombin deficiency, and also discuss puzzling questions and future perspectives regarding this severe inherited thrombophilia. Expert opinion. Although this disorder exerts high clinical heterogeneity, many carriers will need careful and long-term anticoagulation and/or thromboprophylaxis, especially in high-risk situations, such as surgery and pregnancy. Notably, antithrombin concentrates constitute a considerable arsenal for both treatment and prevention of acute venous thrombosis in subjects with antithrombin deficiency. Current evidences are based almost exclusively on retrospective case series, so an integrated functional, biochemical and molecular characterization will be of clinical relevance and guide hematologists' personalized decisions.

Molecular basis of SERPINC1 mutations in Japanese patients with antithrombin deficiency

BACKGROUND

Congenital antithrombin (AT) deficiency, which arises from various SERPINC1 defects, is an autosomal-dominant thrombophilic disorder associated with a high risk of recurrent venous thromboembolism.

PATIENTS/METHODS

We investigated SERPINC1 defects in Japanese patients with congenital AT deficiency who developed venous thromboembolism or had a family history of deep vein thrombosis. We analyzed the full DNA sequences of SERPINC1 exons and exon-intron junctions by PCR-mediated direct sequencing. If no mutation was found, multiplex ligation-dependent probe amplification (MLPA) was conducted for the relative quantification of the copy number of all exons in SERPINC1. If splice-site mutations were detected, mRNA splicing abnormalities were further investigated using an in vitro cell-based exontrap assay.

RESULTS

We identified 19 different SERPINC1 abnormalities, including 8 novel mutations, in 21 Japanese patients with AT deficiency. These abnormalities were distributed as follows: 9 missense mutations (42.9%), 3 nonsense mutations (14.3%), 1 splice-site mutation (4.8%), 2 small insertions (9.5%), 2 deletion mutations (9.5%) and 4 large deletions (19.0%). Cases with large deletions of SERPINC1 included Alu-mediated gene rearrangements and non-Alu-mediated complex gene rearrangements; the latter could conceivably be explained using the fork stalling and template switching (FoSTeS) model.

CONCLUSIONS

We identified a variety of SERPINC1 defects in Japanese patients with AT deficiency. The SERPINC1 mutations detected in patients with type I AT deficiency included single nucleotide missense or nonsense mutations, small intragenic insertions or deletions, and large genomic structural deletions. Large deletions of SERPINC1 were caused by various recurrent or non-recurrent complex genomic rearrangement mutations.

Incidence and features of thrombosis in children with inherited antithrombin deficiency

Pediatric thromboembolism (≤18 years) is very rare (0.07-0.14/10,000/year) but may be more prevalent in children with severe thrombophilia (protein C, protein S or antithrombin deficiency). The aim of this study was to define the prevalence and clinical characteristics of pediatric thrombosis in subjects with inherited antithrombin deficiency. Our observational retrospective multicentric study from two countries recruited 968 patients of any age from 441 unrelated families with genetically, biochemically and functionally characterized antithrombin deficiency. Seventy-three subjects (7.5%) developed thrombosis before 19 years of age. Two high-risk periods for thrombosis were identified: adolescence (12-18 years, n=49) with thrombus localization (lower limb deep venous thrombosis or pulmonary embolism) and triggering factors common to adults (oral contraceptives, surgery or pregnancy); and the neonatal period (<30 days, n=15) with idiopathic thrombosis at unusual sites. The clinical evaluation of pediatric thrombosis in subjects with antithrombin deficiency revealed: i) a high prevalence of cerebral sinovenous thrombosis (n=13, 17.8%), mainly at young age (8 neonates and 4 children <6 years); ii) severe outcome with fatality in six cases (3 neonates, two of them homozygous for p.Leu131Phe). The majority of subjects (76.7%) carried quantitative type I deficiency. This retrospective analysis includes the largest cohort of subjects with inherited antithrombin deficiency so far and provides strong evidence for an increased risk of pediatric thrombosis associated with this thrombophilia (300-fold compared with the general population: 0.41%/year vs. 0.0014%/year, respectively). Our results support testing for antithrombin deficiency in children of affected families, particularly in case of type I deficiency.

Direct oral anticoagulants in patients with venous thromboembolism and thrombophilia: a systematic review and meta-analysis

Essentials We investigated direct oral anticoagulant (DOAC) use in venous thromboembolism and thrombophilia. A comprehensive search identified 10 studies, 8 of which were included in a meta-analysis. DOACs were overall safe and effective in patients with venous thromboembolism and thrombophilia. Efficacy/safety of DOACs was maintained in low-risk antiphospholipid syndrome patient subgroup. SUMMARY: Background Direct oral anticoagulants (DOACs) are increasingly used in acute and long-term treatment of venous thromboembolism (VTE). However, their role in management of thrombophilia-associated VTE is controversial. Methods Through a comprehensive search on MEDLINE, Cochrane Library, and Clinicaltrials.gov, we identified 10 eligible studies, 8 of which reporting data on 1994 thrombophilia patients were included in a random-effects meta-analysis. Eligible studies were phase 2 to 3 randomized controlled trials comparing DOACs to vitamin K antagonists (VKAs) in patients with VTE, including those with thrombophilia. Results Of eight studies included in meta-analysis, four evaluated rivaroxaban, three dabigatran, and one edoxaban. No results could be obtained on apixaban use. The rates of VTE recurrence (RR, 0.70; 95% CI, 0.34-1.44; I2  = 0%) and major/clinically relevant non-major bleeding events (RR, 0.92; 95% CI, 0.62-1.36; I2  = 23%) were similar between thrombophilia patients treated with DOACs compared to VKAs. Results were comparable to findings in patients without known thrombophilia: RR, 1.02; 95% CI, 0.80-1.30; I2  = 46% for VTE recurrence and RR, 0.72; 95% CI, 0.57-0.90; I2  = 84% for major/clinically relevant non-major bleeding events. Conclusions Rates of VTE recurrence and bleeding events were both low and comparable in patients with various thrombophilias receiving either treatment, suggesting that DOACs are an appropriate treatment option in this population. Due to limited data, it is unclear whether these findings apply to specific subgroups such as high-risk antiphospholipid syndrome, uncommon thrombophilias, or the use of apixaban.

Thrombophilia, risk factors and prevention

INTRODUCTION

Fifty-three years after the first description of an inherited prothrombotic condition (antithrombin deficiency), our knowledge on hereditary and acquired causes of hypercoagulability that can predispose carriers to venous thromboembolism (VTE) has greatly improved. Areas covered: Main causes of hereditary thrombophilia are summarized alongside new prothrombotic mutations recently discovered. The main causes of acquired thrombophilia, and namely, antiphospholipid antibody syndrome and hyperhomocysteinemia, are also discussed together with other common acquired prothrombotic states characterized by an increase of procoagulant factors and/or a decrease of natural anticoagulants. Finally, suggestions for thromboprophylaxis in carriers of hereditary thrombophilia according to current guidelines/evidence are made for the most challenging high-risk situations (i.e. surgery, pregnancy, contraception, cancer, economy class syndrome) as well as for the prevention of post-thrombotic syndrome. Expert opinion: A carrier of inherited thrombophilia should be evaluated in the framework of other (genetic and/or acquired) coexisting risk factors for first or recurrent VTE when assessing the need and duration of prevention (primary prophylaxis). Prevention strategies should be tailored to each patient and every situational risk factor. The knowledge of the carriership status of severe thrombophilia in the proband can be important to provide asymptomatic relatives with adequate counseling on thrombophilia screening or primary thromboprophylaxis.

[Risk factors for thromboembolic disease in young women-the role of hormones]

Hormonal exposure in young women increases the risk of venous thromboembolic disease (VTE). Thrombophilia testing is often proposed in women of childbearing age before the initiation of contraception. However, the presence of a familial history of VTE has the potential to be more accurate than the presence of inherited thrombophilia.

OBJECTIVE

To demonstrate an association between the risk of VTE in young women with hormonal exposure (pregnancy or oral contraceptive use) and the presence of a previous episode of VTE in their first-degree relatives, according to whether or not a detectable inherited thrombophilia was present.

METHODS

We will perform a multicenter case-control cross-sectional study. The main risk factor is defined by the presence of a symptomatic VTE in young women with hormonal exposure. The principle variable is the presence of an objectively diagnosed episode of VTE in first-degree relatives. We will need to include 2,200 family members in 440 cases.

EXPECTED RESULTS

We expect to improve understanding of the thrombotic risk in first-degree relatives of patients in hormonal context with or without a past history of VTE.