A prospective cohort study on the absolute risks of venous thromboembolism and predictive value of screening asymptomatic relatives of patients with hereditary deficiencies of protein S, protein C or antithrombin

Analysis of PROC mutations and clinical features in 22 unrelated families with inherited protein C deficiency

Currently, limited information is available in the literature regarding the relationships between PROC mutations and clinical features in Chinese individuals. We aimed to characterize severe congenital Protein C deficiency in 22 unrelated Chinese families in a tertiary hospital by analyzing its clinical manifestation, associated risk factors, and gene mutations. We measured protein C activity and antigen levels for all participants, screened them for mutations in the PROC gene, and analyzed the clinical features of each family to identify commonalities and differences. The analysis revealed a total of 75 individuals with PCD and 16 different PROC mutations, including 12 missense mutations and 4 deletion mutations. Among them, 11 who were compound heterozygotes or homozygotes for mutations tended to develop symptoms at a younger age without any clear triggers. In contrast, the remaining 64 individuals who were heterozygotes for mutations often had clear triggers for their symptoms and experienced a milder course of the disease. It is worth noting that the mutation c.565C > T occurred most frequently, being identified in 8 out of 22 families (36%). Our team also reported five novel mutations, including c.742-744delAAG, c.383G > A, c.997G > A, c.1318C > T, and c.833T > C mutations. The identification of five novel mutations adds to the richness of the Human Genome Database. Asymptomatic heterozygotes are not uncommon, and they are prone to develop symptoms with obvious triggers. The evidence presented strongly suggest that asymptomatic individuals with family history of protein C deficiency can benefit from mutational analysis of PROC gene.

Molecular basis of inherited protein C deficiency results from genetic variations in the signal peptide and propeptide regions

BACKGROUND

Inherited protein C deficiency (PCD) caused by mutations in protein C (PC) gene (PROC) increases the risk of thrombosis. Missense mutations in PC's signal peptide and propeptide have been reported in patients with PCD, but their pathogenic mechanisms, except mutations in R42 residue, remain unclear.

OBJECTIVES

To investigate the pathogenic mechanisms of inherited PCD caused by 11 naturally occurring missense mutations in PC's signal peptide and propeptide.

METHODS

Using cell-based assays, we evaluated the impact of these mutations on various aspects such as activities and antigens of secreted PC, intracellular PC expression, subcellular localization of a reporter protein, and propeptide cleavage. Additionally, we investigated their effect on pre-messenger RNA (pre-mRNA) splicing using a minigene splicing assay.

RESULTS

Our data revealed that certain missense mutations (L9P, R32C, R40C, R38W, and R42C) disrupted PC secretion by impeding cotranslational translocation to the endoplasmic reticulum or causing endoplasmic reticulum retention. Additionally, some mutations (R38W and R42L/H/S) resulted in abnormal propeptide cleavage. However, a few missense mutations (Q3P, W14G, and V26M) did not account for PCD. Using a minigene splicing assay, we observed that several variations (c.8A>C, c.76G>A, c.94C>T, and c.112C>T) increased the incidence of aberrant pre-mRNA splicing.

CONCLUSION

Our findings suggest that variations in PC's signal peptide and propeptide have varying effects on the biological process of PC, including posttranscriptional pre-mRNA splicing, translation, and posttranslational processing. Additionally, a variation could affect the biological process of PC at multiple levels. Except for W14G, our results provide a clear understanding of the relationship between PROC genotype and inherited PCD.

Functional analysis of two abnormal antithrombin proteins with different intracellular kinetics

INTRODUCTION

Hereditary antithrombin (AT) deficiency type I causes venous thrombosis due to decreased levels of AT antigen in the blood. We identified one novel and one known abnormal variant in two unrelated Japanese families with venous thrombosis. In this study, we analyzed the mechanism by which these abnormal variants cause type I AT deficiency.

MATERIALS AND METHODS

Wild-type and variant AT expression vectors were constructed and transiently expressed in human embryonic kidney 293 cells, and AT antigen levels and N-glycosylation of cell lysates and culture medium were evaluated by western blot analysis. Subcellular co-localization of AT was also examined using confocal microscopy, and chase experiments with cycloheximide and MG132 were performed to investigate the degradation pathway of AT variants.

RESULTS

Genetic analysis identified a novel variant, c.613delC (p.Leu205Trpfs⁎79), and the known variant c.283T>C (p.Tyr95His). These AT variants exhibited significantly reduced extracellular secretion compared with the wild-type; N-glycosylation of the AT protein was normal. Co-localization analysis suggested that the transport of these abnormal AT proteins to the Golgi apparatus was impaired. The c.613delC variant was degraded early by the proteasome, suggesting that the c.283T>C variant is stored in the endoplasmic reticulum (ER).

CONCLUSIONS

The AT variants identified here synthesize abnormal AT proteins that exhibit suppressed secretion and impaired transport from the ER to the Golgi apparatus. These results provide clues that could help elucidate the mechanism of type I AT deficiency and facilitate therapy development.

Effect of 10-Day Treatment with 50 mg Prednisolone Once-Daily on Haemostasis in Healthy Men-A Randomised Placebo-Controlled Trial

Synthetic corticosteroids are widely used due to their anti-inflammatory and immunosuppressant effects. Their use has been associated with venous thromboembolism, but it is unknown whether thromboembolism has a causal relationship with corticosteroid treatment. In a randomised, double-blind, placebo-controlled trial in normal to overweight healthy men, the effect of the corticosteroid prednisolone on haemostasis using either 50 mg prednisolone or matching placebo once daily for ten days was investigated. The primary outcome was a change from baseline in the viscoelastic measurement maximal amplitude of clot in kaolin-activated thromboelastography (TEG). Changes from baseline in other TEG measurements, D-dimer, von Willebrand factor (VWF) antigen, and ristocetin cofactor activity (RCo), antithrombin, protein C, prothrombin, fibrinogen, INR, APTT, and platelet count were secondary outcomes. Thirty-four men participated in this study. Compared to placebo, prednisolone treatment did not affect maximal amplitude of clot (difference -0.77 (95% confidence interval (CI) -2.48, 0.94) mm, p = 0.37, missing: n = 2), but it altered VWF antigen (28%, p = 0.0004), VWF:RCo (19%, p = 0.0006), prothrombin (5%, p = 0.05), protein C (31%, p < 0.0001), antithrombin (5%, p = 0.013), and fibrinogen (-15%, p = 0.004). Thus, prednisolone treatment did not alter TEG-assessed maximal amplitude of clot, despite that it affected prothrombotic markers (increased prothrombin, VWF antigen, VWF:RCo, prothrombin, and decreased fibrinogen) and increased antithrombotic markers (protein C and antithrombin).

Antithrombin, Protein C, and Protein S: Genome and Transcriptome-Wide Association Studies Identify 7 Novel Loci Regulating Plasma Levels

BACKGROUND

Antithrombin, PC (protein C), and PS (protein S) are circulating natural anticoagulant proteins that regulate hemostasis and of which partial deficiencies are causes of venous thromboembolism. Previous genetic association studies involving antithrombin, PC, and PS were limited by modest sample sizes or by being restricted to candidate genes. In the setting of the Cohorts for Heart and Aging Research in Genomic Epidemiology consortium, we meta-analyzed across ancestries the results from 10 genome-wide association studies of plasma levels of antithrombin, PC, PS free, and PS total.

METHODS

Study participants were of European and African ancestries, and genotype data were imputed to TOPMed, a dense multiancestry reference panel. Each of the 10 studies conducted a genome-wide association studies for each phenotype and summary results were meta-analyzed, stratified by ancestry. Analysis of antithrombin included 25 243 European ancestry and 2688 African ancestry participants, PC analysis included 16 597 European ancestry and 2688 African ancestry participants, PSF and PST analysis included 4113 and 6409 European ancestry participants. We also conducted transcriptome-wide association analyses and multiphenotype analysis to discover additional associations. Novel genome-wide association studies and transcriptome-wide association analyses findings were validated by in vitro functional experiments. Mendelian randomization was performed to assess the causal relationship between these proteins and cardiovascular outcomes.

RESULTS

Genome-wide association studies meta-analyses identified 4 newly associated loci: 3 with antithrombin levels (GCKR, BAZ1B, and HP-TXNL4B) and 1 with PS levels (ORM1-ORM2). transcriptome-wide association analyses identified 3 newly associated genes: 1 with antithrombin level (FCGRT), 1 with PC (GOLM2), and 1 with PS (MYL7). In addition, we replicated 7 independent loci reported in previous studies. Functional experiments provided evidence for the involvement of GCKR, SNX17, and HP genes in antithrombin regulation.

CONCLUSIONS

The use of larger sample sizes, diverse populations, and a denser imputation reference panel allowed the detection of 7 novel genomic loci associated with plasma antithrombin, PC, and PS levels.

Acute Portal Vein Thrombosis as an Initial Presentation of Protein C Deficiency: A Case Report

Protein C (PC) is an essential vitamin K-dependent protein that regulates thrombosis and hemostasis in the body. A mutation in the PROC gene on chromosome 2q14.3 results in PC deficiency. The clinical presentation of PC deficiency can vary, ranging from a single vein thrombosis to disseminated intravascular coagulation, purpura fulminans, or even life-threatening complications such as sepsis. Here, we present a case of a 37-year-old female who was found to have acute portal vein thrombosis as an initial presentation of PC deficiency. She presented to the hospital with acute onset of abdominal pain associated with nausea, blood-streaked emesis, and bloody bowel movement.

Decreased protein C activity, lower ADAMTS13 antigen and free protein S levels accompanied by unchanged thrombin generation potential in hospitalized COVID-19 patients

INTRODUCTION

COVID-19 is associated with an increased thromboembolic risk. However, the mechanisms triggering clot formation in those patients remain unknown.

PATIENTS AND METHODS

In 118 adult Caucasian severe but non-critically ill COVID-19 patients (median age 58 years; 73 % men) and 46 controls, we analyzed in vitro plasma thrombin generation profile (calibrated automated thrombogram [CAT assay]) and investigated thrombophilia-related factors, such as protein C and antithrombin activity, free protein S level, presence of antiphospholipid antibodies and factor V Leiden R506Q and prothrombin G20210A mutations. We also measured circulating von Willebrand factor (vWF) antigen and a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) antigen and activity. In patients, blood samples were collected on admission to the hospital before starting any therapy, including heparin. Finally, we examined the relationship between observed alterations and disease follow-up, such as thromboembolic complications.

RESULTS

COVID-19 patients showed 17 % lower protein C activity, 22 % decreased free protein S levels, and a higher prevalence of positive results for IgM anticardiolipin antibodies. They also had 151 % increased vWF, and 27 % decreased ADAMTS13 antigens compared with controls (p < 0.001, all). On the contrary, thrombin generation potential was similar to controls. In the follow-up, pulmonary embolism (PE) occurred in thirteen (11 %) patients. They were characterized by a 55 % elevated D-dimer (p = 0.04) and 2.7-fold higher troponin I (p = 0.002) during hospitalization and 29 % shorter time to thrombin peak in CAT assay (p = 0.009) compared to patients without PE.

CONCLUSIONS

In COVID-19, we documented prothrombotic abnormalities of peripheral blood. PE was characterized by more dynamic thrombin generation growth in CAT assay performed on admittance to the hospital.

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.

Identification and functional analysis of three novel genetic variants resulting in premature termination codons in three unrelated patients with hereditary antithrombin deficiency

Hereditary antithrombin (AT) deficiency is an autosomal dominant inherited thrombophilia. In three pedigrees of hereditary type I AT deficiency, we identified novel variants c.126delC (p.Lys43Serfs^*7), c.165C > G (p.Tyr55^*), and c.546delA (p.Lys182Asnfs^*102) in the open reading frame encoding AT in each patient. Each of these aberrant variants leads to premature termination of AT protein synthesis. To investigate whether these abnormal variants are involved in the pathogenesis of type I AT deficiency, we analyzed the function of these variants in HEK293 cells. Results of western blot analysis and immunofluorescence microscopy showed that all abnormal variants were expressed intracellularly, but p.Lys43Serfs^*7 and p.Tyr55^* protein were aggregated in the cells. These three variants were not detected in the spent culture medium, indicating that these novel variants affect protein secretion. In summary, we suggest that these variants in the AT-encoding gene are translated in the cell, but form abnormal proteins that form aggregates and/or inhibit secretion. These results provide insight into novel mechanisms of type I AT deficiency and potential therapies for the condition.

A case of polycystic ovary syndrome with inevitable miscarriage and multi-site venous thrombosis caused by hereditary protein C deficiency

BACKGROUND

Polycystic ovarian syndrome (PCOS) affects up to 18% of reproductive-aged women and raises the risk of venous thromboembolic disease (VTE), due to metabolic features and an apparent fibrinolytic state. Recent studies have shown an increased risk of VTE (1.5- to 2-fold) in patients with PCOS as compared to those without PCOS. Mutations in the Protein C (PC) gene (PROC) lead to deficiency or dysfunction of the protein, Protein C deficiency is the main clotting physiological inhibitor of protein C cofactors, and is a risk factor for venous thrombosis, which can cause a variety of events, including miscarriage. This case report proposes a correlation between PCOS, protein C deficiency, venous thrombosis and inevitable miscarriage.

CASE PRESENTATION

A 33-year-old Chinese woman was diagnosed with Polycystic Ovary Syndrome (PCOS) in 2015. During the course of treatment, she took ethinylestradiol and cyproterone acetate tablets for more than one year. In 2016, she was sent to a hospital for emergency care due to explosive thrombosis (thrombosis in multiple parts of the body and pulmonary thrombosis). In 2020, the patient became pregnant via natural means and came to our hospital for treatment. During the second trimester, she experienced an inevitable miscarriage. High-throughput sequencing (NGS) of peripheral blood lymphocytes revealed that the patient had a protein C deficiency resulting from a heterozygous mutation deletion of 572_574 in exon 7.

CONCLUSION

PC deficiency in conjunction with PCOS and the concomitant use of oral contraceptive (COC) would increase the risk of VTE, especially in the early stages of COC use.

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.

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.

Towards personalized antithrombotic management with drugs and devices across the cardiovascular spectrum

Intravascular thrombus formation and embolization are among the most frequent events leading to a number of cardiovascular conditions with high morbidity and mortality. The underlying causes are stasis of the circulating blood, genetic and acquired coagulation disorders, and reduced antithrombotic or prothrombotic properties of the vascular wall (Virchow's triad). In the venous system, intravascular thrombi can cause venous thrombosis and pulmonary and even peripheral embolism including ischaemic stroke [through a patent foramen ovale (PFO)]. Thrombi in the left atrium and its appendage or ventricle form in the context of atrial fibrillation and infarction, respectively. Furthermore, thrombi can form on native or prosthetic aortic valves, within the aorta (in particular at sites of ulcers, aortic dissection, and abdominal aneurysms), and in cerebral and peripheral arteries causing stroke and critical limb ischaemia, respectively. Finally, thrombotic occlusion may occur in arteries supplying vital organs such the heart, brain, kidney, and extremities. Thrombus formation and embolization can be managed with anticoagulants and devices depending on where they form and embolize and on patient characteristics. Vitamin K antagonists are preferred in patients with mechanical valves, while novel oral anticoagulants are first choice in most other cardiovascular conditions, in particular venous thromboembolism and atrial fibrillation. As anticoagulants are associated with a risk of bleeding, devices such as occluders of a PFO or the left atrial appendage are preferred in patients with an increased bleeding risk. Platelet inhibitors such as aspirin and/or P2Y12 antagonists are preferred in the secondary prevention of coronary artery disease, stroke, and peripheral artery disease either alone or in combination depending on the clinical condition. A differential and personalized use of anticoagulants, platelet inhibitors, and devices is recommended and reviewed in this article.

Anticoagulation Treatment in Venous Thromboembolism: Options and Optimal Duration

Venous thromboembolism (VTE), clinically presenting as deep-vein thrombosis (DVT) or pulmonary embolism (PE), constitutes a major global healthcare concern with severe complications, long-term morbidity and mortality. Although several clinical, genetic and acquired risk factors for VTE have been identified, the molecular pathophysiology and mechanisms of disease progression remain poorly understood. Anticoagulation has been the cornerstone of therapy for decades, but there still are uncertainties regarding primary and secondary VTE prevention, as well as optimal therapy duration. In this review we discuss the role of factor Xa in coagulation cascade and the different choices of anticoagulation therapy based on patients' predisposing risk factors and risk of event recurrence. Further, we compare newer agents to traditional anticoagulation treatment, based on most recent studies and guidelines.

High penetrance of inferior vena cava system atresia in severe thrombophilia caused by homozygous antithrombin Budapest 3 variant: Description of a new syndrome

Atresia of inferior vena cava (IVC) is a rare congenital malformation associated with high risk of venous thrombosis that still has unknown etiology, although intrauterine IVC thrombosis has been suggested to be involved. The identification of IVC atresia in a case with early idiopathic venous thrombosis and antithrombin deficiency caused by the homozygous SERPINC1 c.391C > T variant (p.Leu131Phe; antithrombin Budapest 3) encouraged us to evaluate the role of this severe thrombophilia in this vascular abnormality. We have done a cross-sectional study in previously identified cohorts of patients homozygous for the Budapest 3 variant (N = 61) selected from 1118 patients with congenital antithrombin deficiency identified in two different populations: Spain (N = 692) and Hungary (N = 426). Image analysis included computed tomography and phlebography. Atresia of the IVC system was observed in 17/24 cases (70.8%, 95% confidence interval [CI]: 48.9%-87.3%) homozygous for antithrombin Budapest 3 with available computed tomography (5/8 and 12/16 in the Spanish and Hungarian cohorts, respectively), 16 had an absence of infrarenal IVC and one had atresia of the left common iliac vein. All cases with vascular defects had compensatory mechanisms, azygos-hemiazygos continuation or double IVC, and seven also had other congenital anomalies. Short tandem repeat analysis supported the specific association of the IVC system atresia with SERPINC1. We show the first evidence of the association of a severe thrombophilia with IVC system atresia, supporting the possibility that a thrombosis in the developing fetal vessels is the reason for this anomaly. Our hypothesis-generating results encourage further studies to investigate severe thrombophilic states in patients with atresia of IVC.

Multiple arterial and venous thromboembolism in a male patient with hereditary protein C deficiency: A case report

RATIONALE

Hereditary protein C deficiency has a high prevalence in Asian populations, being the important risk factor associated with thrombophilia. Traditionally, conservative medication is the first choice for patients with hereditary protein C deficiency. However, there are few reports on whether aggressive surgical treatment can be performed when patients continue to develop life-threatening ischemic symptoms after adequate anticoagulant and thrombolytic therapy.

PATIENT CONCERNS

A 40-year-old male presented with right lower extremity pain for 1 week.

DIAGNOSIS

Computed tomography angiography (CTA) of lower extremity indicated arterial embolization of the right superficial femoral artery. Vascular ultrasonography showed old extensive thrombus in the deep vein of the left lower extremity. Electrocardiogram reported old anterior myocardial infarction. Sequencing of the gene encoding protein C (PROC) gene revealed that a heterozygous in-frame deletion mutation (c.577-579delAAG, p.192delK). Based on these findings, the diagnosis of hereditary protein C deficiency was made.

INTERVENTIONS

The patient was given low-molecular-weight heparin (LMWH) anticoagulation and urokinase treatment immediately. Then we performed the Fogarty catheter embolectomy with about 18.5 cm thrombus being removed and utilized the balloon catheter to dilate the anterior tibial artery. Despite given adequate anticoagulant and thrombolytic therapy postoperatively, the patient still had new thrombosis, and eventually underwent arterial embolectomy and amputation.

OUTCOMES

The patient was discharged with good wound healing and continued rivaroxaban treatment at a dose of 20 mg daily. The patient was followed-up monthly until 1 year: there was no adverse ischemic events occurred.

LESSONS

Aggressive surgical treatment may be the effective attempt for life-saving when conservative treatment as the first choice had unsatisfactory results in hereditary protein C deficiency patients. The novel oral anticoagulants (NOACs) could be more suitable than warfarin for the treatment and prevention of recurrence in patients with hereditary protein C deficiency.

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.

Pulmonary Embolism in Pregnancy

Even though venous thromboembolism is a leading cause of maternal mortality in high-income countries, there are limited high-quality data to assist clinicians with the management of pulmonary embolism in this patient population. Diagnosis, prevention, and treatment of pregnancy-associated pulmonary embolism are complicated by the need to consider fetal, as well as maternal, well-being. Recent studies suggest that clinical prediction rules and D-dimer testing can reduce the need for diagnostic imaging in a subset of patients. Low-molecular-weight heparin is the preferred anticoagulant for both prophylaxis and treatment in this setting. Direct oral anticoagulants are contraindicated during pregnancy and in breastfeeding women. Thrombolysis or embolectomy should be considered for pregnant women with pulmonary embolism complicated by hemodynamic instability. Treatment of pregnancy-associated pulmonary embolism should be continued for at least 3 months, including 6 weeks postpartum. Management of anticoagulants at the time of delivery should involve a multidisciplinary individualized approach that uses shared decision making to take patient and caregiver values and preferences into account.

Thrombophilia testing in patients with portal vein thrombosis

Portal vein thrombosis (PVT) is a rare but severe condition. Several risk factors predispose to PVT. However, it remains unclear to which degree thrombophilia contributes to the risk of PVT and whether PVT patients should be routinely referred for thrombophilia testing. The aim of the present study was to investigate the prevalence of thrombophilia in PVT patients to clarify the relevance of thrombophilia testing in PVT patients. Clinical data and results from thrombophilia investigations were systematically obtained from all PVT patients referred to Centre for Hemophilia and Thrombosis, Aarhus University Hospital, Denmark for thrombophilia testing between 1^st of January 2010 and 31^st of December 2018 (n = 93). The investigated thrombophilias included factor V Leiden and prothrombin G20210A mutations, deficiency of protein S, protein C and antithrombin, antiphospholipid syndrome, and increased levels of factor VIII. The prevalence of thrombophilia was compared to healthy controls obtained from previously published data on thrombophilia distribution in cohorts of the Western European adult general population. Comparing PVT patients with healthy controls, significantly increased odds of presence of lupus anticoagulant (crude odds ratio (OR) 6.2, 95% confidence interval (CI) 1.8-20.6) were found, whereas no significantly increased odds of inherited thrombophilia were demonstrated. In conclusion, routine testing for inherited thrombophilia in PVT patients does not seem indicated. However, PVT patients should still be tested for antiphospholipid antibodies because patients meeting the criteria for antiphospholipid syndrome preferentially should receive vitamin K antagonists as anticoagulant therapy.

Protein C deficiency; PROC gene variants in a Danish population

INTRODUCTION

Protein C deficiency is a heritable thrombophilia caused by numerous different genetic alterations in the protein C (PROC) gene. We aimed to identify variants causing protein C deficiency in a Danish population.

MATERIAL AND METHODS

Sanger sequencing of the PROC gene was performed in 20 probands and 26 relatives. In total, 30participants were previously diagnosed with protein C deficiency. Protein C activity was measured by a chromogenic substrate method (N = 40) and antigen level by an enzyme-linked immunosorbent assay (N = 26).

RESULTS

Ten different single nucleotide variants were detected in 13 probands (65%) and in seven of the relatives previously diagnosed with protein C deficiency. Five variants were novel. The median protein C activity level was lower in participants with an identified variant (50% (range: 38-75%)) than in protein C deficient participants without a variant (65% (range: 36-73%); P = 0.18). A protein C activity of 57% resulted in the highest detection rate (12/13 (92%)). Likewise, the median antigen level was lower in participants with detectable variants than in participants without (49% (range: 35-99%) vs 70% (range: 41-101%); P = 0.09). No difference was found in venous thromboembolism (VTE) prevalence comparing participants with (12/20 (60%)) and without (7/10 (70%)) a variant (P = 0.59).

CONCLUSION

In a Danish population, a PROC gene variant was identified in 67% of participants previously diagnosed with protein C deficiency. Five variants were novel. The study confirmed an association between biochemical severity and the presence of a PROC gene variant. The VTE risk did not seem to differ between protein C deficient participants with and without a variant.

Pregnancy-related thrombosis risk in patients with protein C deficiency and comparison with pregnant women with heterozygous factor V Leiden mutation

: The risk of pregnancy-related venous thromboembolism is high in patients with inherited thrombophilia. The aim of this study was to compare the risk of pregnancy related-venous thromboembolism of women with protein C (PC) deficiency to patients with heterozygous factor V Leiden mutation. 145 consecutive pregnant women with confirmed PC deficiency or heterozygous factor V Leiden mutation were prospectively enrolled in the study. Lyon venous thromboembolism-risk score was used to individually tailor antithrombotic prophylaxis. The use of a validated clinical score presents the advantage to have a homogenous management of the venous thromboembolism risk in patients having similar risk factors. 53 pregnancies with PC deficiency were compared with 190 pregnancies in heterozygous factor V Leiden mutation carriers. 50% of the patients with PC deficiency and 64% of the heterozygous factor V Leiden mutation carriers were asymptomatic. According to the Lyon-venous thromboembolism risk score, 50% of patients with PC deficiency and 51% of heterozygous factor V Leiden carriers did not received any antepartum heparin prophylaxis. 34 and 37% of patients respectively received heparin prophylaxis during the third trimester only. No venous thromboembolism was observed in patients with PC deficiency and one postpartum venous thromboembolism occurred in a patient with heterozygous factor V Leiden. In the absence of randomized controlled clinical studies, we report here a large prospective series of pregnant women with PC deficiency. In our cohort, no difference of outcome, in terms of venous thromboembolism, was observed between pregnant women with PC deficiency and those with heterozygous factor V Leiden. Based on our results, low-molecular-weight heparin prophylaxis should not be mandatory in all pregnant women with PC deficiency. Similar prophylaxis strategies may be applied to women with factor V Leiden mutation or PC deficiency.

American Society of Hematology 2018 guidelines for management of venous thromboembolism: venous thromboembolism in the context of pregnancy

BACKGROUND

Venous thromboembolism (VTE) complicates ∼1.2 of every 1000 deliveries. Despite these low absolute risks, pregnancy-associated VTE is a leading cause of maternal morbidity and mortality.

OBJECTIVE

These evidence-based guidelines of the American Society of Hematology (ASH) are intended to support patients, clinicians and others in decisions about the prevention and management of pregnancy-associated VTE.

METHODS

ASH formed a multidisciplinary guideline panel balanced to minimize potential bias from conflicts of interest. The McMaster University GRADE Centre supported the guideline development process, including updating or performing systematic evidence reviews. The panel prioritized clinical questions and outcomes according to their importance for clinicians and patients. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to assess evidence and make recommendations.

RESULTS

The panel agreed on 31 recommendations related to the treatment of VTE and superficial vein thrombosis, diagnosis of VTE, and thrombosis prophylaxis.

CONCLUSIONS

There was a strong recommendation for low-molecular-weight heparin (LWMH) over unfractionated heparin for acute VTE. Most recommendations were conditional, including those for either twice-per-day or once-per-day LMWH dosing for the treatment of acute VTE and initial outpatient therapy over hospital admission with low-risk acute VTE, as well as against routine anti-factor Xa (FXa) monitoring to guide dosing with LMWH for VTE treatment. There was a strong recommendation (low certainty in evidence) for antepartum anticoagulant prophylaxis with a history of unprovoked or hormonally associated VTE and a conditional recommendation against antepartum anticoagulant prophylaxis with prior VTE associated with a resolved nonhormonal provoking risk factor.

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.

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.

Safe childbirth for a type 1 antithrombin-deficient woman with novel mutation in the SERPINC1 gene undergoing antithrombin concentrate therapy

: Inherited antithrombin (AT) deficiency is an autosomal dominant thrombotic disorder. We encountered a case of inherited type I AT deficiency and identified the causative mutation; a novel c.7430A>G missense mutation in the SERPINC1 gene in which tyrosine was substituted for cysteine at the 292nd amino acid. A recombinant AT protein with the 7430A>G mutation was not detected in cell lysates or culture supernatants. And then, our patient without personal or family history of thrombosis was pregnant woman with asymptomatic AT deficiency. Our patient treated with only AT concentrate therapy during pregnancy and she was able to safely give birth naturally and avoid thrombosis. We believe that this therapy for pregnant woman with asymptomatic AT deficiency is effective and safety as anticoagulant therapy during pregnancy.

Venous thromboembolism prophylaxis using the Caprini score

Venous thromboembolism (VTE) including pulmonary embolism (PE) and deep vein thrombosis (DVT) is one of the leading causes of preventable cardiovascular disease in the United States (US) and is the number one preventable cause of death following a surgical procedure. Post-operative VTE is associated with multiple short and long-term complications. We will focus on reviewing the many faces of VTE in detail as they represent common challenging scenarios in clinical practice.

The influence of specific mutations in the AT gene (SERPINC1) on the type of pregnancy related complications

BACKGROUND

Inherited antithrombin (AT) deficiency is a rare autosomal dominant disorder, caused by mutations in the SERPINC1 gene. The most common clinical presentation in AT deficient patients includes venous thrombosis and pulmonary embolism, while the association of AT deficiency and its effect on the development of pregnancy complications has been less studied. The aim of our research was to evaluate the effect of AT deficiency types, determined by genotyping, on pregnancy outcomes.

METHODS

A retrospective cohort study included 28 women with AT deficiency, and their 64 pregnancies were analyzed.

RESULTS

With regard to live birth rate, a significant difference was observed among women who were carriers of different SERPINC1 mutations, as the rate varied from 100% in cases of type I to the extremely low rate of 8% for women with type II HBS (AT Budapest 3) in the homozygous variant, P = 0.0005. All pregnancies from the type I group, even untreated ones, resulted in live births. In women with AT Budapest 3 in homozygous variant the overall live birth rate increased to 28.5% in the treated pregnancies. In this group the highest incidence of fetal death was observed of 62%; repeated fetal losses in 30%; fetal growth restriction in 22% and placental abruption in 7% of all pregnancies.

CONCLUSION

Our study results indicate a difference between type I and type II AT deficiency. The risk of pregnancy related VTE was equally present in both groups, except for AT Budapest 3 in the heterozygous variant, while adverse pregnancy outcomes were strictly related to type II, especially AT Budapest 3 in the homozygous variant.

Preventing venous thromboembolism during pregnancy and postpartum: crossing the threshold

When should a patient with a known thrombophilia or prior venous thromboembolism (VTE) receive low-molecular-weight heparin (LMWH) prophylaxis during pregnancy and/or the postpartum period? Accurately predicting thrombotic and bleeding risks and knowing what to do with this information is at the heart of decision-making in these challenging scenarios. This article will explore the concept of a risk threshold from clinician and patient perspectives and provide guidance for the use of antepartum and postpartum LMWH prophylaxis in women with a known thrombophilia or prior VTE. Advice for the management of LMWH prophylaxis use around labor and delivery is also reviewed.

In families with inherited thrombophilia the risk of venous thromboembolism is dependent on the clinical phenotype of the proband

The utility of laboratory investigation of relatives of individuals with inherited thrombophilia is uncertain. To assess the risk of venous thromboembolism (VTE) among the carriers, we investigated a family cohort of 1,720 relatives of probands with thrombophilia who were evaluated because of VTE (n=1,088), premature arterial thrombosis (n=113), obstetric complication (n=257), or universal screening before pregnancy or hormonal contraception or therapy (n=262); 968 relatives were carriers of thrombophilia. A first deep venous thrombosis (DVT) occurred in 44 carriers and 10 non-carriers during 37,688 and 29,548 observationyears from birth, respectively. The risk of DVT among the carriers compared with non-carriers was estimated as a hazard ratio (HR). If the proband had VTE and factor V Leiden (FVL) and/or prothrombin (PT)20210A, the HR for DVT was 2.77 (95%CI 1.21–4.82) in the carriers overall, and 5.54 (95%CI 3.20–187.00) in those homozygous or double heterozygous for FVL and PT20210A. If the proband had VTE and a deficiency of antithrombin (AT), protein C or S, the HR for DVT was 5.14 (95%CI 0.88–10.03) in the carriers overall, and 12.86 (95%CI 2.46–59.90) in those with AT deficiency. No increase in risk was found among the carriers who were relatives of the probands who were evaluated for reasons other than VTE. In conclusion, familial investigation for inherited thrombophilia seems justified for probands with previous VTE, but appears of doubtful utility for the relatives of probands without VTE. This should be taken with caution regarding families with deficiency of natural anticoagulants, given the low number of cases analysed.

Circulating microparticles and the risk of thrombosis in inherited deficiencies of antithrombin, protein C and protein S

Many subjects carrying inherited thrombophilic defects will never experience venous thromboembolism (VTE) while other individuals developed recurrent VTE with no known additional risk factors. High levels of circulating microparticles (MP) have been associated with increased risk of VTE in patients with factor V Leiden and prothrombin G20210A mutation, suggesting a possible contribution of MP in the hypercoagulability of mild genetic thrombophilia. The role of MP as additional risk factor of VTE in carriers of natural clotting inhibitors defects (severe thrombophilia) has never been assessed. Plasma levels of annexin V-MP, endothelial-derived MP (EMP), platelet-derived MP (PMP), tissue factor-bearing MP (TF+) and the MP procoagulant activity (PPL) were measured in 132 carriers of natural anticoagulant deficiencies (25 antithrombin, 63 protein C and 64 protein S defect) and in 132 age and gender-matched healthy controls. Carriers of natural anticoagulant deficiencies, overall and separately considered, presented with higher median levels of annexin V-MP, EMP, PMP, TF+MP and PPL activity than healthy controls (p< 0.001, < 0.001, < 0.01, 0.025 and 0.03, respectively). Symptomatic carriers with a previous episode of VTE had significantly higher median levels of annexin-V MP than those without VTE (p=0.027). Carriers with high levels of annexin V-MP, EMP and PMP had an adjusted OR for VTE of 3.36 (95 % CI, 1.59 to 7.11), 9.26 (95 % CI, 3.55 to 24.1) and 2.72 (95 %CI, 1.16 to 6.38), respectively. Elevated levels of circulating MP can play a role in carriers of mild and severe inherited thrombophilia. The clinical implications of this association remain to be defined.

Clinical and laboratory characteristics of antithrombin deficiencies: A large cohort study from a single diagnostic center

INTRODUCTION

Inherited antithrombin (AT) deficiency is a heterogeneous disease. Due to low prevalence, only a few studies are available concerning genotype-phenotype associations. The aim was to describe the clinical, laboratory and genetic characteristics of AT deficiency in a large cohort including children and to add further laboratory data on the different sensitivity of functional AT assays.

PATIENTS AND METHODS

Non-related AT deficient patients (n=156) and their family members (total n=246) were recruited. Clinical and laboratory data were collected, the mutation spectrum of SERPINC1 was described. Three different AT functional assays were explored.

RESULTS

Thirty-one SERPINC1 mutations including 11 novel ones and high mutation detection rate (98%) were detected. Heparin binding site deficiency (type IIHBS) was the most frequent (75.6%) including AT Budapest3 (ATBp3), AT Padua I and AT Basel (86%, 9% and 4% of type IIHBS, respectively). Clinical and laboratory phenotypes of IIHBS were heterogeneous and dependent on the specific mutation. Arterial thrombosis and pregnancy complications were the most frequent in AT Basel and AT Padua I, respectively. Median age at the time of thrombosis was the lowest in ATBp3 homozygotes. The functional assay with high heparin concentration and pH7.4 as assay conditions had low (44%) sensitivity for ATBp3 and it was insensitive for AT Basel and Padua I.

CONCLUSION

Type IIHBS deficiencies behave differently in clinical and laboratory phenotypes from each other and from other AT deficiencies. Heparin concentration and pH seem to be the key factors influencing the sensitivity of AT functional assays to IIHBS.

A case that illustrates the challenges of managing pregnant patients with antithrombin deficiency: More questions than answers

Using an illustrative case of a patient with antithrombin (AT) deficiency who developed a recurrent venous thromboembolism (VTE) in pregnancy despite therapeutic low-molecular-weight heparin (LMWH), we highlight what is known in the literature and address areas of controversy through a series of questions around the case. The questions we address include the role of anti-Xa monitoring for patients with past VTE on antepartum LMWH, what treatment regimen is recommended for pregnant patients who develop a recurrent VTE while on therapeutic anticoagulation, the role of antepartum AT concentrate prophylaxis, and the management of labor/delivery, epidural anesthesia and postpartum anticoagulation. We also describe practical considerations for use of AT concentrate, including teaching our patient to self-infuse AT concentrate at home with support of a hemophilia treatment center (HTC), and the direct and indirect costs of AT concentrate for secondary prophylaxis.

SERPINC1 gene mutations in antithrombin deficiency

Existing evidence suggests that in most cases antithrombin deficiency can be explained by mutations in its gene, SERPINC1. We investigated the molecular background of antithrombin deficiency in a single centre family cohort study. We included a total of 21 families comprising 15 original probands and sixty-six relatives, 6 of who were surrogate probands for the genetic analysis. Antithrombin activity and antigen levels were measured. The heparin-antithrombin binding ratio assay was used to distinguish between the different subtypes of type II antithrombin deficiency. SERPINC1 mutations were detected by direct sequencing of all 7 exons and regulatory regions, and multiplex ligation-dependent probe amplification. Eighty-six per cent of the families had a detrimental SERPINC1 gene mutation that segregated in the family. We detected 13 different SERPINC1 gene mutations of which 5 were novel. Among all these mutations, 44% was associated with type I deficiency, whereas the remainder was associated with type II heparin binding site (11%), type II pleiotropic effect (33%), type II reactive site (6%) or had the antithrombin Cambridge II mutation (6%). The current study reports several novel SERPINC1 mutations, thereby adding to our knowledge of the molecular background of antithrombin deficiency. Finally, our results point out the importance of future research outside the conventional SERPINC1 gene approach.

A novel frameshift mutation leading to inherited type I antithrombin deficiency

Inherited antithrombin (AT) deficiency is an autosomal dominant thrombotic disorder. We encountered a case of inherited type I AT deficiency and identified the mutation responsible; a novel 5406delA mutation in the SERPINC1 gene appeared to have caused a frameshift with premature termination at amino acid +283. The recombinant AT protein including 5406delA was not detected in cell lysates or culture supernatants. These results will contribute to the creation of an accurate database and define the molecular basis for AT deficiency.

Thrombophilia Screening: Universal, Selected, or Neither?

The utility of thrombophilia testing in clinical practice is still a matter of debate because studies have not shown a benefit in the reduction of recurrent venous thromboembolism (VTE) risk in patients with thrombosis, despite the clearly higher VTE risk for first thrombosis. Screening for thrombophilia is indicated in selected patients. Particularly in selected young patients, especially women of childbearing age, the knowledge of the genetic thrombophilic defect may help in specific situations to decrease the risk of VTE events. Avoidance of modifiable risk factors and/or prophylactic thromboembolic procedures may be evaluated in selected patients. A comprehensive workup including personal and familial history, clinical examination, and laboratory test results including hereditary thrombophilia remains helpful in assessing the cumulative risk and the management of this group of selected patients.

Impact of high risk thrombophilia status on recurrence among children and adults with VTE: An observational multicenter cohort study

BACKGROUND

Antithrombin [AT]-, protein C [PC]- or protein S [PS]-deficiency [D] constitutes a major risk factor for venous thromboembolism [VTE]. Primary study objective was to evaluate if the clinical presentation at first VTE onset differs between children and adults and to compare the individual recurrence risk among patients with respect to age at onset and their thrombophilia status ATD, PCD or PSD.

METHODS/PATIENTS/RESULTS

In 137 of 688 consecutively enrolled pediatric and adult VTE patients we calculated the absolute risk of VTE recurrence and event-free-survival adjusted for thrombophilia and positive family VTE history. At first VTE children manifested i) with a lower rate of pulmonary embolism, ii) a higher rate of cerebral vascular events or multiple VTEs, and iii) showed a higher proportion of unprovoked VTE compared to adolescents and adults. Adult patients reported more often a positive VTE history compared to younger study participants. The adjusted odds of recurrence in adults was 2.05 compared to children.

CONCLUSION

At disease manifestation children and adults differ with respect to i) thrombotic locations, ii) percentage of unprovoked versus provoked VTE, and iii) different rates of positive VTE family histories. Furthermore, adults showed a two-fold increase risk of VTE recurrence compared to children.

Guidance for the evaluation and treatment of hereditary and acquired thrombophilia

Thrombophilias are hereditary and/or acquired conditions that predispose patients to thrombosis. Testing for thrombophilia is commonly performed in patients with venous thrombosis and their relatives; however such testing usually does not provide information that impacts management and may result in harm. This manuscript, initiated by the Anticoagulation Forum, provides clinical guidance for thrombophilia testing in five clinical situations: following 1) provoked venous thromboembolism, 2) unprovoked venous thromboembolism; 3) in relatives of patients with thrombosis, 4) in female relatives of patients with thrombosis considering estrogen use; and 5) in female relatives of patients with thrombosis who are considering pregnancy. Additionally, guidance is provided regarding the timing of thrombophilia testing. The role of thrombophilia testing in arterial thrombosis and for evaluation of recurrent pregnancy loss is not addressed. Statements are based on existing guidelines and consensus expert opinion where guidelines are lacking. We recommend that thrombophilia testing not be performed in most situations. When performed, it should be used in a highly selective manner, and only in circumstances where the information obtained will influence a decision important to the patient, and outweigh the potential risks of testing. Testing should not be performed during acute thrombosis or during the initial (3-month) period of anticoagulation.

Hypoglycosylation is a common finding in antithrombin deficiency in the absence of a SERPINC1 gene defect

Essentials We investigated the molecular base of antithrombin deficiency in cases without SERPINC1 defects. 27% of cases presented hypoglycosylation, transient in 62% and not restricted to antithrombin. Variations in genes involved in N-glycosylation underline this phenotype. These results support a new form of thrombophilia. Click here to listen to Dr Huntington's perspective on thrombin inhibition by the serpins

SUMMARY

Background Since the discovery of antithrombin deficiency, 50 years ago, few new thrombophilic defects have been identified, all with weaker risk of thrombosis than antithrombin deficiency. Objective To identify new thrombophilic mechanisms. Patients/methods We studied 30 patients with antithrombin deficiency but no defects in the gene encoding this key anticoagulant (SERPINC1). Results A high proportion of these patients (8/30: 27%) had increased hypoglycosylated forms of antithrombin. All N-glycoproteins tested in these patients (α1-antitrypsin, FXI and transferrin) had electrophoretic, HPLC and Q-TOF patterns indistinguishable from those of the congenital disorders of glycosylation (rare recessive multisystem disorders). However, all except one had no mental disability. Moreover, intermittent antithrombin deficiency and hypoglycosylation was recorded in five out of these eight patients, all associated with moderate alcohol intake. Genetic analysis, including whole exome sequencing, revealed mutations in different genes involved in the N-glycosylation pathway. Conclusions Our study provides substantial and novel mechanistic insights into two disease processes, with potential implications for diagnosis and clinical care. An aberrant N-glycosylation causing a recessive or transient antithrombin deficiency is a new form of thrombophilia. Our data suggest that congenital disorders of glycosylation are probably underestimated, especially in cases with thrombosis as the main or only clinical manifestation.

Impact of high-risk thrombophilia status on recurrence among children with a first non-central-venous-catheter-associated VTE: an observational multicentre cohort study

Deficiency of antithrombin (AT), protein C (PC) or protein S (PS) constitutes a major risk factor for venous thromboembolism (VTE). Individuals at high risk for recurrence who benefit from screening need to be identified. The primary study objective was to determine the individual recurrence risk among children with a first non-central-venous-catheter-associated VTE with respect to their thrombophilia status and to evaluate if the clinical presentation at first VTE onset differs between children with AT, PC or PS deficiency versus no thrombophilia. We calculated the absolute risk of VTE recurrence and event-free-survival adjusted for thrombophilia, age, sex and positive family VTE history in 161 consecutively enrolled paediatric VTE patients. The presence of a deficiency relative to no thrombophilia was evaluated as a potential predictor of recurrence. Predictors for recurrence were AT deficiency (hazard ratio/95% CI: 6·5/2·46-17·2) and female gender (2·6/1·1-6·35). The annual recurrence rates (95% CIs) were 5·4% (2·6-10) in AT-deficient children, 1·3% (0·3-3·8) in patients with PC deficiency, 0·7% (0·08-2·4) in the PS-deficient cohort and 0·9% (0·4-1·8) in patients with no thrombophilia. Positive family VTE history or combined thrombophilias did not predict recurrence. Given the overall annual incidence rate of recurrence of 1·5% we suggest screening for AT deficiency in children with VTE.

Interaction of Hereditary Thrombophilia and Traditional Cardiovascular Risk Factors on the Risk of Arterial Thromboembolism

Background—

Hereditary thrombophilia is associated with a slightly increased risk of arterial thromboembolism (ATE). Whether hereditary thrombophilia interacts with traditional cardiovascular risk factors on the risk of ATE has yet to be established.

Methods and Results—

A total of 1891 individuals belonging to 4 family cohorts from the Netherlands were included in the analyses. Five hereditary thrombophilic defects, including factor V Leiden, prothrombin G20210A defect, and deficiencies of the natural anticoagulants (ie, antithrombin, protein C, and protein S), were assessed, and data on risk factors and previous ATE were collected. Thrombophilia was associated with elevated risk of ATE (hazard ratio =1.74, 95% confidence interval, 1.18–2.58; P =0.005). Overall, the association of thrombophilia with ATE tended to be stronger in the presence of traditional cardiovascular risk factors, especially the synergistic effect of thrombophilia with diabetes mellitus was striking (hazard ratio of thrombophilia–ATE association was 1.41 in nondiabetics versus 8.11 in diabetics). Moreover, the association of thrombophilia with ATE tended to be stronger in females and before the age of 55 years as compared with males and individuals >55 years of age, respectively.

Conclusions—

Thrombophilia is associated with ATE. This association may be stronger in the presence of traditional cardiovascular risk factors in particular in individuals with diabetes mellitus. Future studies on thrombophilia–ATE risk should focus on high-risk populations with high prevalence of traditional cardiovascular risk factors.