Management of antithrombin deficiency: an update for clinicians

Antithrombin: Deficiency, Diversity, and the Future of Diagnostics

Our healthcare system provides reactive sick-care, treating patients after symptoms have appeared by prescription of generic and often suboptimal therapy. This strategy brings along high costs and high pressure which is not sustainable. Alternatively, P5 healthcare is proposed focusing on five key elements: prevention, personalization, prediction, participation, psychocognition, however, changes in current clinical care pathways are required, for which antithrombin deficiency is a prime example. Hereditary antithrombin deficiency (ATD) is a genetic disorder, for which screening is instigated after a thrombotic episode. Current diagnostic tests for ATD lack sensitivity and refinement to correctly classify patients, and generic treatments are prescribed. A molecular understanding of ATD through a molecular diagnostic test that analyzes all clinically relevant features of antithrombin is required. Here, clinically relevant molecular characteristics of antithrombin, the diversity of antithrombin (deficiency) in heath and disease, and the strengths and weaknesses of antithrombin tests are reviewed. A mass spectrometry test that molecularly characterizes a patients antithrombin proteoforms harbors the highest potential to improve the clinical pathway for ATD. Application of this MS-based test in a future enhanced clinical pathway will improve patient management and outcome through molecular characterization of antithrombin and enables the promise of P5 healthcare for ATD.

The novel SERPINC1 missense mutation c.1148 T > A (p.L383H) causes hereditary antithrombin deficiency and thromboembolism in a Chinese family: a case report

BACKGROUND

Hereditary antithrombin deficiency, an autosomal-dominant thrombotic disease caused by a SERPINC1 gene deficiency, is extremely rare, although it is the leading cause of hereditary thrombophilias. Herein we report a novel SERPINC1 gene mutation in a Chinese family and one case of pulmonary embolism associated with the mutation. We also discuss the latest diagnostic and treatment strategies for antithrombin deficiency.

CASE PRESENTATION

The 33-year-old Chinese male proband had a pulmonary embolism and there was no evidence of thromboembolism in the other family members. In the pulmonary embolism case, treatment with nadroparin calcium combined with warfarin failed; however, rivaroxaban was effective. No emboli were evident in the follow-up computed tomography pulmonary angiography. Antithrombin activity fluctuated approximately 50% during hospitalization and follow-up. The antithrombin activity of the proband, his 58-year-old father, and his 5-year-old son was significantly low (44-48%). A novel missense variant c.1148 T > A (p.L383H) in the SERPINC1 gene was identified in these three family members. The pathogenesis predictions from Mutation-Taster, Provean, and SIFT were "disease-causing," "deleterious," and "damaging," respectively.

CONCLUSION

The novel c.1148 T > A (p.L383H) pathogenic mutation in the SERPINC1 gene updated the gene mutation spectrum of hereditary antithrombin deficiency. Direct oral anticoagulation with rivaroxaban may be a more effective and selective anticoagulant in patients with hereditary antithrombin deficiency over warfarin or heparin.

Higher dose of rivaroxaban for the treatment of venous thromboembolism in a 15-year-old Asian child with antithrombin deficiency: A case report and literature review

RATIONALE

Deficiency in antithrombin (AT) can significantly increase the risk of venous thromboembolism (VTE). However, there is insufficient data on the efficacy and safety of anticoagulants in patients with AT deficiency, especially in children. In addition, Asian populations typically require a lower dose of rivaroxaban, and this may be even more pronounced in Asian children. This case aims to explore the potential efficacy and safety of a higher dose of rivaroxaban in an Asian child with AT deficiency and VTE.

PATIENT CONCERNS

A 15-year-old boy was referred to our center with severe deep vein thrombosis progression. The primary concern was the effective management of the thromboembolic events while minimizing the risk of bleeding, given the patient's young age and AT deficiency.

DIAGNOSES

The patient was diagnosed with pulmonary embolism and deep vein thrombosis with AT deficiency.

INTERVENTIONS

The patient was treated with a higher dose of rivaroxaban, which was 15 mg twice a day for 3 weeks, followed by 20 mg per day for 6 months, which was a relatively high dose for an Asian child.

OUTCOMES

During the follow-up period, the patient did not experience any VTE events or bleeding events.

LESSONS

This case provides additional data on the efficacy and safety of direct oral factor Xa inhibitors in patients with VTE and AT deficiency. It suggests that for Asian children with AT deficiency, considering a higher dose of rivaroxaban could be beneficial, especially when the children's height, weight, and age are close to adults.

How we treat severe inherited antithrombin deficiency: lessons from cases homozygous for the Budapest 3 variant

BACKGROUND

Antithrombin deficiency represents one of the most severe inherited thrombophilias. Albeit a rare disorder, available knowledge suggests that antithrombin deficiency is underestimated due to the limitations of current diagnostic algorithms. The high clinical variability of this patient population may be another cause of underdiagnosis. Heterozygous type I (quantitative) variants are normally associated with a severe thrombophilic phenotype, while heterozygous type II (qualitative) variants are heterogeneous, including heparin-binding site defects, which are mild/moderate and the most prevalent. Antithrombin Budapest 3 (p.Leu131Phe) is the most frequent type II/heparin-binding site deficiency in Europe, particularly in the Roma population, with a remarkable existence of homozygous subjects.

OBJECTIVES

To determine the clinical features, diagnostic procedures, and management of patients with severe antithrombin deficiency, leveraging the study of cases homozygous for the antithrombin Budapest 3 variant.

METHODS

Patients were selected from 699 subjects with antithrombin deficiency and recruited over 25 years from reference centers in Spain, Belgium, and Hungary.

RESULTS

Guided by 2 illustrative cases with homozygous antithrombin Budapest 3, we report the spectrum and clinical management of patients with this disorder. These cases, with very low antithrombin activity (<20%) and juvenile and recurrent venous thromboembolism, recapitulate numerous issues that one might encounter when treating patients with antithrombin deficiency. In addition, special clinical scenarios for which no formal evidence-based guidelines exist might be found more frequently in these patients, including heparin resistance, vena cava anomalies, and obstetric complications.

CONCLUSION

Expert proposals on the optimal management of these controversial areas, as well as future perspectives, are also formulated.

Unraveling High Altitude-Induced Thromboembolic Disorders: Polycythemia or Complex Mechanisms?

Kansara, Nikunj Kumar, Anurag Timothy, Rijesh Unnithan, and Manas Chatterjee. Unraveling high altitude-induced thromboembolic disorders: polycythemia or complex mechanisms?. High Alt Med Biol. 00:00-00, 2024. Background: Thromboembolic disorders (TEDs) occurring at high altitudes due to exposure to hypoxic environments pose a significant challenge for clinicians in high-altitude area. Hypobaric hypoxia often leads to acquired erythrocytosis, which is believed to increase the incidence of thrombosis. This study aims to examine the relationship between thromboembolic events and erythrocytosis. Methodology: A prospective study was conducted, including all the patients admitted to Siachen hospital for TEDs from January 01, 2022, to December 31, 2022. Data on height, duration of the stay, hemoglobin (Hb), and packed cell volume levels at the time of admission were recorded. Results: A total of 35 cases were enrolled during the study period. The average age of the patients was 29.10 years (standard deviation: 6.06). The mean deployment height was 17,300 ft, with a range of 12,000 ft-21,600 ft. The average duration of stay was 73 days, ranging from 7 to 162 days. The mean Hb level was 18 g/dl (SD: 2.64), with a range of 12.4 g/dl-22.4 g/dl. Twenty-five cases of thrombotic events (71.4%) occurred with normal Hb levels (<17.5 mg/dl), compared with 10 cases (28.6%) with Hb levels >17.5 mg/dl. Conclusion: Prolonged stays at high altitudes and exposure to hypobaric hypoxia are major stressors. The study suggests that it is not elevated Hb levels, but rather the body's lack of an appropriate physiological response, that contributes to the development of thromboembolic events.

Clinical and functional characterization of p.Lys322stop variant in the SERPINC1 gene causing severe thrombophilia

BACKGROUND

Identification of mutations in the SERPINC1 has illuminated the intricate pathways underlying antithrombin (AT) deficiency. Our group identified a variation in the SERPINC1 gene (c.964 A > T, p.Lys322stop) and further investigated the mechanism of this variant causing AT deficiency.

METHODS

Multiple in silico tools were utilized to predict the conservation of mutations and their impact on the AT structure. The coagulation state was evaluated using the thrombin generation assay. Recombinant AT was overexpressed in HEK293T cells. Intracellular kinetics and extracellular secretion of recombinant AT-K322* were scrutinized by RT-qPCR, Western blotting, ELISA, and immunocytofluorescence.

RESULTS

Analysis of conservation in silico indicated 43 out of the 143 amino acids deleted byAT-K322* in AT were highly conserved across homologous species. In vitro expression experiments showed that there was no significant difference in mRNA levels between the mutant (AT-K322*) and wild-type (AT-WT) forms of the protein. The truncated AT-K322* protein was clearly detected in cell lysates, but not in the culture medium.

CONCLUSION

AT-K322* resulted in the generation of a truncated protein, which in turn affected the secretion of AT, ultimately leading to AT deficiency.

Predictive Value of Serum Immune-Inflammatory Markers for Adverse Pregnancy Outcomes in Pregnant Women with Thrombophilia: A Retrospective Cohort Study

Background

Thrombophilia combined with pregnancy poses significant risks for adverse pregnancy outcomes. Unfortunately, there are no indicators at high risk for predicting adverse pregnancy outcomes. This study investigates the predictive efficiency of serum immune-inflammatory markers on adverse pregnancy outcomes.

Methods

This retrospective cohort study includes 223 pregnant women diagnosed with thrombophilia who delivered at the Fujian Provincial Hospital South Branch from January 2022 to April 2024. Clinical information and pregnancy outcomes were collected. The systemic immune-inflammation index (SII), systemic inflammation response index (SIRI), and lactate dehydrogenase (LDH) were calculated using blood samples. The relationship and predictive accuracy between immune-inflammatory markers and adverse pregnancy outcomes were analyzed.

Results

In this study, 50 (22.4%) patients had adverse pregnancy outcomes. Significant differences were observed in neutrophils counts, monocytes counts, LDH, SII, and SIRI levels between the adverse pregnancy outcome groups (APOs) and the control groups (P<0.05). The area under the receiver operating characteristic (ROC) curve analysis revealed that SII (AUC=0.762), SIRI (AUC=0.764), and LDH (AUC=0.732) had high predictive values for adverse pregnancy outcomes. Notably, the combined model had the highest AUC of 0.805. Multivariate logistic regression identified SII had the highest odd ratio (OR) (OR=8.512; 95% CI(3.068-23.614)), followed by LDH (OR=4.905; 95% CI (1.167-11.101)), SIRI (OR=3.549; 95% CI(0.847-8.669)), and neutrophils count (OR=1.726; 95% CI (0.563-2.938)) as independent risk factors for adverse outcomes.

Conclusion

Elevated levels of immune-inflammatory markers such as SII, SIRI, and LDH level are strong predictors of adverse pregnancy outcomes in thrombophilia-complicated pregnancies. These markers are significantly associated with maternal-neonatal outcomes. Our findings underscore the importance of monitoring immune-inflammatory markers in pregnant women with thrombophilia to improve maternal and neonatal outcomes.

Atypical pulmonary thromboembolism caused by the mutation site SERPINC1 of the antithrombin III gene: A case report

BACKGROUND

Deficiency of natural anticoagulant antithrombin was first reported as a genetic risk factor for venous thromboembolism, antithrombin III (AT III) is encoded by the serpin family C member 1 (SERPINC1) gene, consisting of 432 amino acids, including 3 disulfide bonds and 4 possible glycosylation sites. Studies have shown that hereditary AT deficiency increases the incidence of venous thromboembolism by up to 20 times.

CASE PRESENTATION

The case presented a 27-year-old young man with no acquired risk factors and a sudden onset of right lower extremity venous thrombosis and pulmonary embolism. A heterozygous mutation in gene SERPINC1 of c.1154-14G>A was detected in the patient, which is a deleterious mutation resulting in reduced AT III activity and increased risk of thrombotic events. The patient received anticoagulant therapy for approximately 5 months, and the thrombus gradually dissolved and no recurrent thrombotic events occurred during follow-up.

DISCUSSION

AT deficiency is a rare autosomal dominant genetic disease, they are mainly divided into 2 types according to the different effects on the structure or function of the encoded protein. The patient had a mutation in the SERPINC1 gene (c.1154-14G>A). Several cases of this type of mutation have been reported since 1991, and it is classified as AT deficiency type I.

CONCLUSION

Thrombosis in patients with antithrombin deficiency is often unpredictable and can lead to fatal pulmonary embolism. Early genetic testing for hereditary thrombophilia in venous thromboembolism patients without obvious high-risk factors is critical. Long-term anticoagulation treatment is an effective treatment, for this type of type I AT III deficiency combined with pulmonary embolism patients, warfarin is an effective anticoagulant drug.

Antithrombin Levels and Heparin Responsiveness during Venoarterial Extracorporeal Membrane Oxygenation: A Prospective Single-center Cohort Study

BACKGROUND

Unfractionated heparin, administered during venoarterial extracorporeal membrane oxygenation to prevent thromboembolic events, largely depends on plasma antithrombin for its antithrombotic effects. Decreased heparin responsiveness seems frequent on extracorporeal membrane oxygenation; however, its association with acquired antithrombin deficiency is poorly understood. The objective of this study was to describe longitudinal changes in plasma antithrombin levels during extracorporeal membrane oxygenation support and evaluate the association between antithrombin levels and heparin responsiveness. The hypothesis was that extracorporeal membrane oxygenation support would be associated with acquired antithrombin deficiency and related decreased heparin responsiveness.

METHODS

Adults receiving venoarterial extracorporeal membrane oxygenation were prospectively included. All patients received continuous intravenous unfractionated heparin using a standardized protocol (target anti-Xa 0.3 to 0.5 IU/ml). For each patient, arterial blood was withdrawn into citrate-containing tubes at 11 time points (from hour 0 up to day 7). Anti-Xa (without dextran or antithrombin added) and antithrombin levels were measured. The primary outcome was the antithrombin plasma level. In the absence of consensus, antithrombin deficiency was defined as a time-weighted average of antithrombin less than or equal to 70%. Data regarding clinical management and heparin dosage were collected.

RESULTS

Fifty patients, including 42% postcardiotomy, were included between April 2020 and May 2021, with a total of 447 samples. Median extracorporeal membrane oxygenation duration was 7 (interquartile range, 4 to 12) days. Median antithrombin level was 48% (37 to 60%) at baseline. Antithrombin levels significantly increased throughout the follow-up. Time-weighted average of antithrombin levels was 63% (57 to 73%) and was less than or equal to 70% in 32 (64%) of patients. Overall, 45 (90%) patients had at least one antithrombin value less than 70%, and 35 (70%) had at least one antithrombin value less than 50%. Antithrombin levels were not significantly associated with heparin responsiveness evaluated by anti-Xa assay or heparin dosage.

CONCLUSIONS

Venoarterial extracorporeal membrane oxygenation support was associated with a moderate acquired antithrombin deficiency, mainly during the first 72 h, that did not correlate with heparin responsiveness.

EDITOR’S PERSPECTIVE

Pulmonary thromboembolism associated with hereditary antithrombin III deficiency: A case report

BACKGROUND

Thrombophilia is a coagulation disorder closely associated with venous thromboembolism. Hereditary antithrombin III (AT III) deficiency is a type of genetic thrombophilia. In China, genetic thrombophilia patients mainly suffer from deficiencies in AT III, protein S, and protein C. Multiple mutations in the serpin family C member 1 (SERPINC1) can affect AT III activity, resulting in thrombosis.

CASE PRESENTATION

This case presented a 17-year-old adolescent female who developed lower extremity venous thrombosis and subsequently pulmonary embolism (PE) following a right leg injury. A missense mutation in gene SERPINC1 of c.331 T > C, p.S111P was detected on the patient, resulting in a decreased AT III activity and an elevated risk of thrombosis. The patient received anticoagulation treatment for approximately 5 months. During follow-up, the blood clot gradually dissolved, and there have been no recurrent thrombotic events reported thus far.

DISCUSSION

Hereditary AT deficiency can be classified into two types based on the plasma levels of the enzymatic activity and antigen. Type I is a quantitative defect, while Type II is a qualitive defect. Until 2021, 486 SERPINC1 gene mutations have been registered, more than 18% of which are point mutations. The SERPINC1 mutation c.331 T > C in was firstly reported in 2017, which was classified into type I AT III deficiency.

CONCLUSION

Hereditary thrombophilia is a coagulation disorder with a high omission diagnostic rate. Minor mutations in the SERPINC1 gene can also lead to hereditary AT III deficiency, which in turn can cause PE. We emphasized the importance of etiological screening for hereditary thrombophilia in venous thromboembolism patients without obvious high-risk factors. Long-term anticoagulation treatment and avoidance of potential thrombosis risk factors are critical for such patients.

Research into New Molecular Mechanisms in Thrombotic Diseases Paves the Way for Innovative Therapeutic Approaches

Thrombosis is a multifaceted process involving various molecular components, including the coagulation cascade, platelet activation, platelet-endothelial interaction, anticoagulant signaling pathways, inflammatory mediators, genetic factors and the involvement of various cells such as endothelial cells, platelets and leukocytes. A comprehensive understanding of the molecular signaling pathways and cell interactions that play a role in thrombosis is essential for the development of precise therapeutic strategies for the treatment and prevention of thrombotic diseases. Ongoing research in this field is constantly uncovering new molecular players and pathways that offer opportunities for more precise interventions in the clinical setting. These molecular insights into thrombosis form the basis for the development of targeted therapeutic approaches for the treatment and prevention of thrombotic disease. The aim of this review is to provide an overview of the pathogenesis of thrombosis and to explore new therapeutic options.

Comparison of antithrombin activity assays in detection of patients with heparin binding site antithrombin deficiency: systematic review and meta-analysis

Antithrombin (AT) deficiency increases the risk for venous thromboembolism, therefore, a highly sensitive assay to identify this condition is crucial. The aim of this paper was to perform a meta-analysis comparing AT activities measured by different AT activity assays in patients with heparin binding site AT deficiency. In addition, the diagnostic sensitivity of selected assays was compared depending on the available data. An extensive literature search was performed considering results with publication date up to July 10, 2021. Seven relevant English-language observational studies, comparing AT activity measured by different AT activity assays in Caucasian Europeans with either the AT Budapest III or AT Padua I mutation were included in meta-analyses. There was no significant difference in AT activity between Labexpert and Innovance in patients with AT Budapest III (P = 0.567) and AT Padua I (P = 0.265), while AT activity determined by HemosIL was significantly higher compared to Innovance for both mutations (AT Budapest III: P < 0.001; AT Padua I: P < 0.001). These results are in line with the results of comparison of diagnostic sensitivity. In patients with AT Budapest III, the AT activity was also higher when measured with Berichrom compared to Innovance (P = 0.002), however, the results of comparison of diagnostic sensitivity across studies were variable. No significant difference (P = 0.117) in AT activity as well as diagnostic sensitivity was observed between Sta-Stachrom and Innovance. The results of our study suggest that Innovance, Labexpert and Sta-Stachrom are the most sensitive activity assays for detection of AT Budapest III and AT Padua I, whereas HemosIL showed considerably lower sensitivity for these two variants. As revealed in our study, the diagnostic sensitivity of AT activity assays to type II heparin binding site AT deficiency is different, and in some assays mutation dependent.

Case report: A case of new mutation in SERPINC1 leading to thrombotic microangiopathy

Introduction: Hereditary antithrombin-III deficiency can significantly increase the risk for thrombosis, which is common in limb deep vein and pulmonary cases. However, thrombotic microangiopathy (TMA) caused by hereditary antithrombin deficiency is rare. Case Presentation: We reported the case of a 32-year-old Chinese female patient with TMA with renal injury caused by decreased antithrombin-III activity due to a new mutation (chr1-173884049 c.50A>G) in SERPINC1, which encodes antithrombin-III. In this case, the patient had no history of relevant drug use, diabetes, or monoclonal plasma cells in the bone marrow puncture. Consequently, TMA of the kidney was considered secondary to hereditary antithrombin-III deficiency. Gene detection was the only clue that led us to suspect that TMA was caused by hereditary antithrombin deficiency. Conclusion: Our findings indicated that for patients with repeated findings of antithrombin-III activity less than 50%, the possibility of antithrombin-III deficiency and complete gene detection must be considered immediately after excluding the use of anticoagulants and lack of availability to facilitate early detection, diagnosis, and intervention.

High prevalence of thrombophilic risk factors in patients with central retinal artery occlusion

INTRODUCTION

Central retinal artery occlusion (CRAO) is a common cause of blindness and visual morbidity. In the majority of cases, it is related to thrombotic embolism. Nevertheless, the role of inherited or acquired thrombophilic risk factors in CRAO pathogenesis has not been comprehensively studied.

METHODS

In 126 CRAO patients (66 [52.4%] men, median age 55 [range: 18-80] years) and 107 matched controls (56 [52.3%] men, median age 53 [range: 34-78] years) we evaluated classical atherosclerotic risk factors, including serum lipid profile and glucose level, analyzed intima-media complex thickness (IMT) of external carotid arteries, and performed transthoracic echocardiography. Furthermore, we established the prevalence of inherited and acquired thrombophilic risk factors, such as factor V Leiden (FVL) and prothrombin 20210 G/A genetic variants, plasma activity of factor (F) VIII, protein C and antithrombin activity, and free protein S levels. We also assessed the presence of antiphospholipid antibodies (APLA) and evaluated blood homocysteine in all enrolled subjects. Additionally, we estimated the occurrence of Val34Leu polymorphism of the A subunit of coagulation factor XIII (FXIII-A) in both groups as a potential thrombosis-protecting factor.

RESULTS

Among traditional atherosclerotic risk components, obesity/overweight and hypercholesterolemia were the most common in the CRAO group and occurred in 103 (81.7%) and 85 (67.5%) patients, respectively. CRAO patients also had elevated IMT and altered echocardiographic parameters, indicating diastolic cardiac dysfunction. In thrombophilia investigations, at least one laboratory risk factor occurred in 72.2% (n = 91) of CRAO patients, with APLA as the most frequent, detected in 38.1% (n = 48) of them (almost seven times more frequent than in controls, p < 0.001). Deficiencies in protein C activity and free protein S levels were also common in the CRAO group, reported in 17.5% (n = 22) and 19.8% (n = 25) of patients, respectively. Interestingly, among two analyzed prothrombotic genetic variants, only the FVL was related to CRAO, with the allelic frequency 2.4 times more prevalent than in controls (p = 0.044). Finally, the CRAO group was characterized by hyperhomocysteinemia, almost twice as common as in controls (p = 0.026). Antithrombin deficiency, elevated FVIII, and FXIII-A Val34Leu polymorphism were not associated with CRAO.

CONCLUSIONS

Our findings suggest that thrombophilia plays a vital role in the pathogenesis of CRAO. Thus, proper laboratory screening should be considered in the primary and secondary prevention of those episodes, with implementing appropriate therapy as needed.

Argatroban Resistance and Successful Adjunctive Anticoagulation for Cerebral Venous Sinus Thrombosis WithSERPINC1Mutation

Objectives

Anticoagulation therapy for cerebral venous sinus thrombosis (CVST) with antithrombin (AT) deficiency due toSERPINC1mutation does not often yield the expected outcomes. Argatroban may be effective for thrombophilia caused bySERPINC1mutation. However, argatroban resistance deserves attention.

Methods

We report a case of a 19-year-old man who was admitted to the hospital with sudden headache, nausea, vomiting, and eye swelling for 3 days. Brain MRI on admission showed multifocal CVST.

Results

SERPINC1mutation (exon1, c.40delA: [p.R14Gfs*17]) combined with hereditary AT deficiency (AT activity was 50% [reference range: 80%–120%]) was detected in this patient. A high dose of anticoagulation treatment with argatroban did not improve the activated partial thromboplastin time (APTT) level to the target range (1.5–3 times over the initial baseline level) for this case. We chose adjunctive anticoagulation (argatroban-combined low-molecular-weight heparin), and the APTT gradually reached the target level. At 3-month follow-up, no recurrence of headache or any systemic hemorrhage was found and the ultrasonography of the optic nerve sheath showed normal. Magnetic resonance black blood thrombosis imaging suggested thrombus absorption.

Discussion

Argatroban resistance may be associated with thrombin receptor saturation and deserves attention. The use of adjunctive anticoagulants may be the optimum strategy during acute and subacute phases of CVST with AT deficiency due toSERPINC1mutation.

Usefulness and Limitations of Multiple Ligation-Dependent Probe Amplification in Antithrombin Deficiency

Multiplex ligation-dependent probe amplification (MLPA) identifies genetic structural variants in SERPINC1 in 5% of cases with antithrombin deficiency (ATD), the most severe congenital thrombophilia. Our aim was to unravel the utility and limitations of MLPA in a large cohort of unrelated patients with ATD (N = 341). MLPA identified 22 structural variants (SVs) causing ATD (6.5%). MLPA did not detect SVs affecting introns (four cases), and the diagnosis was inaccurate in two cases according to long-range PCR or nanopore sequencing. MLPA was used to detect possible hidden SVs in 61 cases with type I deficiency with single nucleotide variations (SNVs) or small insertion/deletion (INDEL). One case had a false deletion of exon 7, as the 29-bp deletion affected an MLPA probe. We evaluated 32 variants affecting MLPA probes: 27 SNVs and 5 small INDELs. In three cases, MLPA gave false-positive results, all diagnosed as deletions of the affected exon: a small INDEL complex, and two SNVs affecting MLPA probes. Our study confirms the utility of MLPA to detect SVs in ATD, but also shows some limitations in detecting intronic SVs. MLPA renders imprecise and false-positive results for genetic defects which affect MLPA probes. Our results encourage the validation of MLPA results.

Exploring the Role of Antithrombin in Nephrotic Syndrome-Associated Hypercoagulopathy: A Multi-Cohort Study and Meta-Analysis

BACKGROUND

Nephrotic syndrome is associated with an acquired hypercoagulopathy that is thought to drive its predisposition for venous thromboembolism. Previous studies have suggested that urinary antithrombin (AT) loss leading to acquired AT deficiency is the primary mechanism underlying this hypercoagulopathy, but this hypothesis has not been directly tested. The objectives of this study were to test the influence of AT levels on hypercoagulopathy in nephrotic syndrome patient samples and perform meta-analyses to evaluate the likelihood of AT deficiency in patients with nephrotic syndrome.

METHODS

Samples from three independent nephrotic syndrome cohorts were analyzed. AT antigen and activity assays were performed using ELISA and amidolytic assays, respectively. Plasma thrombin generation, albumin, and urine protein-to-creatinine ratios were determined using established methods. Meta-analyses were performed by combining these new data with previously published data.

RESULTS

AT levels were not consistently related to either plasma albumin or proteinuria. AT was quantitatively related to hypercoagulopathy in adult nephrotic syndrome, whereas AT activity was inconsistently associated with hypercoagulopathy in childhood nephrotic syndrome. Notably, hypercoagulopathy did not differ between patients with normal AT levels and those with levels below the threshold used to define clinical AT deficiency (<70%). Moreover, ex vivo AT supplementation did not significantly alter hypercoagulopathy in AT-deficient plasma samples. The meta-analyses demonstrated that AT deficiency was not a uniform feature of nephrotic syndrome and was more common in children than adults.

CONCLUSIONS

These data suggest that AT deficiency plays only a limited role in the mechanisms underlying the acquired hypercoagulopathy of nephrotic syndrome. Moreover, AT deficiency was not present in all patients with nephrotic syndrome and was more likely in children than adults despite the higher risk for venous thromboembolism in adults than children.

Identification and characterization of two SERPINC1 mutations causing congenital antithrombin deficiency

BACKGROUND

Antithrombin (AT) is the main physiological anticoagulant involved in hemostasis. Hereditary AT deficiency is a rare autosomal dominant thrombotic disease mainly caused by mutations in SERPINC1, which was usually manifested as venous thrombosis and pulmonary embolism. In this study, we analyzed the clinical characteristics and screened for mutant genes in two pedigrees with hereditary AT deficiency, and the functional effects of the pathogenic mutations were evaluated.

METHODS

Candidate gene variants were analyzed by next-generation sequencing to screen pathogenic mutations in probands, followed by segregation analysis in families by Sanger sequencing. Mutant and wild-type plasmids were constructed and transfected into HEK293T cells to observe protein expression and cellular localization of SERPINC1. The structure and function of the mutations were analyzed by bioinformatic analyses.

RESULTS

The proband of pedigree A with AT deficiency carried a heterozygous frameshift mutation c.1377delC (p.Asn460Thrfs*20) in SERPINC1 (NM000488.3), a 1377C base deletion in exon 7 resulting in a backward shift of the open reading frame, with termination after translation of 20 residues, and a different residue sequence translated after the frameshift. Bioinformatics analysis suggests that the missing amino acid sequence caused by the frameshift mutation might disrupt the disulfide bond between Cys279 and Cys462 and affect the structural function of the protein. This newly discovered variant is not currently included in the ClinVar and HGMD databases. p.Arg229* resulted in a premature stop codon in exon 4, and bioinformatics analysis suggests that the truncated protein structure lost its domain of interaction with factor IX (Ala414 site) after the deletion of nonsense mutations. However, considering the AT truncation protein resulting from the p.Arg229* variant loss a great proportion of the molecule, we speculate the variant may affect two functional domains HBS and RCL and lack of the corresponding function. The thrombophilia and decreased-AT-activity phenotypes of the two pedigrees were separated from their genetic variants. After lentiviral plasmid transfection into HEK293T cells, the expression level of AT protein decreased in the constructed c.1377delC mutant cells compared to that in the wild-type, which was not only reduced in c.685C > T mutant cells but also showed a significant band at 35 kDa, suggesting a truncated protein. Immunofluorescence localization showed no significant differences in protein localization before and after the mutation.

CONCLUSIONS

The p.Asn460Thrfs*20 and p.Arg229* variants of SERPINC1 were responsible for the two hereditary AT deficiency pedigrees, which led to AT deficiency by different mechanisms. The p.Asn460Thrfs*20 variant is reported for the first time.

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.

Factor V Leiden, Factor II, Protein C, Protein S, and Antithrombin and Ischemic Strokes in Young Adults: A Meta-Analysis

Ischemic strokes are one of the leading causes of death worldwide. The aim of this meta-analysis is to elaborate on the role of inherited predisposition to thrombophilia in the etiology of ischemic strokes in young adults. The keywords factor V Leiden (FVL), factor II, prothrombin (PT), protein C (PC), protein S (PS), antithrombin (AT), ischemic stroke, and young were used to search different databases. We selected studies with participants who were between 18 and 65 years. A total of 104 studies were eligible for inclusion in the meta-analysis. All the studied genetic markers were risk factors for ischemic stroke according to our results (FVL OR = 1.74; PT OR = 1.95; PC OR = 10.20; PS OR = 1.74; AT OR = 3.47; p < 0.05). There was moderate heterogeneity for most of the results, and subgroup analyses were conducted by dividing the studies according to the geographic location, gender ratio, and selection criteria of the performed study. There were no significant differences between the groups, but different geographic location was a probable source of heterogeneity. All of the studied markers-FVL, prothrombin, PC, PS, and AT-were significantly associated with increased risk of ischemic stroke in young adults and, if tested, could improve the quality of care.

Inherited antithrombin deficiency caused by a mutation in the SERPINC1 gene: A case report

RATIONALE

Inherited antithrombin deficiency (ATD) is a major cause of thrombotic deficiency. Genetic testing is of great value in the diagnosis of hereditary thrombophilia. Herein, we report a case of inherited ATD admitted to our hospital. We include the results of genealogy and discuss the significance of genetic testing in high-risk groups of hereditary thrombophilia.

PATIENT CONCERNS

A 16-year-old male patient presented with chest tightness, shortness of breath, wheezing, and intermittent fever (up to 39 °C) after strenuous exercise for 2 weeks. He also had a cough with white sputum with a small amount of bright red blood in the sputum and occasional back pain.

DIAGNOSES

The blood tests showed that the patient's antithrombin III concentration and activity were both significantly reduced to 41% and 43.2%, respectively. Enhanced chest computed tomography scans showed pulmonary infarction in the lower lobe of the right lung with multiple embolisms in the bilateral pulmonary arteries and branches. Lower vein angiography revealed a contrast-filling defect of the inferior vena cava and left common iliac vein. Thrombosis was considered as a differential diagnosis. His father and his uncle also had a history of thrombosis. The patient was diagnosed with inherited ATD. Further, peripheral venous blood samples of the family members were collected for whole-exome gene sequencing, and Sanger sequencing was used to verify the gene mutation site in the family. The patient and his father had a SERPINC1 gene duplication mutation: c.1315_1345dupCCTTTCCTGGTTTTTAAGAGAAGTTCCTC (NM000488.4).

INTERVENTIONS

An inferior vena cava filter was inserted to avoid thrombus shedding from the lower limbs. Urokinase was injected intermittently through the femoral vein cannula for thrombolysis. Heparin combined with warfarin anticoagulant therapy was sequentially administered. After reaching the international normalized ratio, heparin was discontinued, and oral warfarin anticoagulant therapy was continued. After discharge, the patient was switched to rivaroxaban as oral anticoagulation therapy.

OUTCOMES

The patient's clinical symptoms disappeared. reexamination showed that the thrombotic load was less than before, and the inferior vena cava filter was then removed.

LESSONS

By this report we highlight that gene detection and phenotypic analysis are important means to study inherited ATD.

Five Challenging Cases of Hereditary Antithrombin Deficiency Characterized by Thrombosis or Complicated Pregnancy

Hereditary antithrombin deficiency (ATD) is a rare autosomal dominant condition (estimated prevalence 1:500-1:5000). Most ATD patients have AT activity levels 40-60% of normal. We present treatments for venous thromboembolism (VTE) in five cases of hereditary ATD. Four patients had a family history of ATD, and one had a de novo mutation. The majority of patients had a VTE while on prophylactic anticoagulation. AT concentrate augmentation was added in these cases to treat the VTE and for prophylaxis against further episodes. Two patients had significant bleeding events, one had permanent physical sequelae. Two of the patients were pregnant. VTE is a common cause of morbidity and mortality during pregnancy. Although low molecular weight heparins are the drugs of choice during pregnancy, this treatment was inadequate in one patient (developed VTE on therapy). These cases emphasize the need to screen for ATD in young patients (<55 years) presenting with VTE. AT augmentation therapy may be necessary in patients inadequately treated with conventional anticoagulants. Careful monitoring and individualized care are needed in ATD patients, especially those with demonstrated bleeding tendencies.

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.

Management of Antithrombin Deficiency in Pregnancy

Antithrombin (AT) deficiency is a high-risk thrombophilia and a rare condition. The risk of venous thromboembolism (VTE) is increased in AT-deficient women during pregnancy and the postpartum period and is especially high in women with a prior history of VTE. A thorough assessment of VTE risk is recommended in pregnant AT-deficient women, comprising the degree and type of AT deficiency, genetic mutations, personal and family history, and additional preexisting or pregnancy-specific risk factors. Due to a lack of adequate study data, there is limited guidance on the management of AT deficiency in pregnancy, including the need for prophylactic anticoagulation, the appropriate dose of low-molecular-weight heparin (LMWH), and the role of AT substitution. LMWH is the medication of choice for the pharmacological prophylaxis and treatment of VTE in pregnancy. Patients with a history of VTE should receive full-dose LMWH during pregnancy and the postpartum period. AT concentrates are a treatment option when anticoagulation is withheld in potentially high-risk events such as childbirth, bleeding, or surgery and in cases of acute VTE despite the use of therapeutic dose anticoagulation. Women with AT deficiency should be counseled at specialized centers for coagulation disorders or vascular medicine, and close cooperation between obstetricians and anesthesiologists is warranted before delivery and during the peripartum period.

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 2 new SERPINC1 variants, p.Glu227Lys and p.Asn224His, in 4 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 2 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 for 1 hour at 41°C. Moreover, the β glycoform of the variants, lacking 2 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 posttranslational 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.

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.

Thrombin generation capacity is enhanced by low antithrombin activity and depends on the activity of the related coagulation factors

Background

Supplementation with antithrombin (AT) concentrates is now common in the treatment of congenital and acquired AT deficiency. However, there is no established consensus on the target and timing of supplementation. We aimed to elucidate the effects of AT deficiency on the balance between coagulation activation and inhibition using a thrombin generation assay as in vitro global assay.

Methods

Samples were prepared by admixing commercially acquired AT-deficient plasma with < 1% AT activity with pooled normal plasma. The AT activity in each sample was adjusted to 100, 90, 70, 50, 40, 30, 10, 5, and < 1%. A thrombin generation assay was performed in each sample. AT concentrate-spiked samples were also prepared by adjusting the AT activities in four types of the concentrates: one recombinant and three plasma-derived AT concentrates. The final targeted AT activities in the samples were adjusted to 100, 50, 30, and 5% by spiking each concentrate into the AT-deficient plasma. We also prepared samples with five levels of prothrombin time (PT) % in coagulation factors with the AT activity fixed at 30% by dilution by mixing AT-deficient plasma and normal plasma with Owren’s veronal buffer to adjust the coagulation factor activities in several proportions. The theoretical target PT% values were 100, 66, 50, 40, and 30%. A thrombin generation assay was performed on all samples.

Results

The ability to generate thrombin depended on the AT activity, and the amount of thrombin generation was increased as AT was decreased. Additionally, the amount of thrombin generation was changed significantly when AT activity was ≤ 50%, indicating that AT suppressed thrombin generation. In particular, thrombin generation was remarkable when AT activity was < 30%, and it can be assumed that the prognosis is poor due to organ failure from thrombotic tendency.

Conclusions

The results presented in this basic research were found to be consistent with the clinical findings to date. The mechanism by which 30–50% of AT activity is set as the clinical boundary was elucidated by the thrombin generation assay.

Prevention of venous thromboembolism in pregnant women with congenital antithrombin deficiency: a retrospective study of a candidate protocol

BACKGROUND

The best thromboprophylaxis for pregnant women with congenital antithrombin deficiency (CAD) is controversial.

OBJECTIVE

To clarify the effectiveness of a protocol for venous thromboembolism (VTE) prevention in pregnant women with CAD.

METHODS

Women at high risk of VTE were administered antithrombin concentrate and heparin after conception, whereas those at low risk of VTE were administered heparin alone until delivery. All women received antithrombin concentrate at delivery except for one who was diagnosed with CAD.

RESULTS

Ten women had CAD, including one in the high-risk group and nine in the low-risk group. No women had VTE at delivery as per the protocol for VTE prevention. Almost all women had increased antithrombin activity before delivery followed by maintenance at ≥ 70% due to antithrombin concentrate administration. VTE prophylaxis during and after delivery was successful in all women with CAD. However, one woman in the low-risk group did not receive heparin and developed VTE induced by severe hyperemesis at 9 gestational weeks, before the diagnosis of CAD. Women in the high-risk group received antithrombin concentrate after delivery but had increased D-dimer levels at postpartum.

CONCLUSIONS

Our protocol to prevent VTE in pregnant women with CAD is safe and effective.

Cardiac Arrest Due to Pulmonary Embolism After Posterior Spinal Fusion in a Patient With Acute Paraplegia Caused by a Metastatic Spinal Tumor Associated With Congenital Antithrombin III Deficiency

Congenital antithrombin (AT) III deficiency has a high incidence of deep vein thrombosis and pulmonary embolism due to reduced anticoagulation. In this study, we report a case of a patient who experienced cardiac arrest due to pulmonary embolism after emergency posterior spinal fusion for acute paraplesia due to a metastatic spinal tumor associated with AT III deficiency. A 49-year-old man with a history of familial AT III deficiency visited our hospital due to difficulty in walking caused by a progressive paralysis of the lower limbs. Clinical examination revealed multiple bone metastases due to prostate cancer and spinal cord compression caused by a pathological fracture of the T1 vertebral body. He had low AT III activity levels and high D-dimer levels. The following day, he underwent posterior spinal decompression and fusion. However, he had pulmonary embolism with cardiac arrest three days after surgery. He recovered without sequelae after emergency thrombectomy following resuscitation. Patients with AT III deficiency who cannot walk due to a metastatic spinal tumor inevitably develop deep vein thrombosis and pulmonary embolism. To avoid lethal pulmonary embolism, preventing deep vein thrombosis should be prioritized before surgery, even in the presence of acute progressive paraplegia.

The relationship between insulin sensitivity and serum antithrombin 3 activity in patients with type 2 diabetes

BACKGROUND

Antithrombin 3 (AT3) is a physiological inhibitor of thrombin, and serum AT3 activity was found to decrease at the status of type 2 diabetes (T2D). T2D was presented with an increased risk of thrombotic complications at the background of impaired insulin sensitivity. The aim of this study was to investigate the relationship between insulin sensitivity indices and serum AT3 activity in patients with T2D.

METHODS

We conducted a cross-sectional study in patients with T2D who consented to participate in the study at the Endocrinology Department of Affiliated 2 Hospital of Nantong University from January 2015 to June 2018. All patients received serum AT3 activity test and 75 g oral glucose tolerance test (OGTT). Basal and systemic insulin sensitivity were assessed by homeostasis model assessment of insulin resistance (HOMA-IR) and Matsuda index (ISIMatsuda), respectively, from the OGTT. And other relevant clinical data were also collected.

RESULTS

Total of 1612 patients with T2D were enrolled in the study, with a mean age of 58.67 ± 13.09 years and a median diabetes duration of 6 years (interquartile range, 1-10 years). Across ascending quartiles of serum AT3 activity, HOMA-IR progressively decreased, while ISIMatsuda progressively increased (all P for trend < 0.001). Moreover, serum AT3 activity was negatively correlated with HOMA-IR (r = -0.189, P < 0.001) and positively correlated with ISIMatsuda (r = 0.221, P < 0.001). After adjusting for other metabolic risk factors, hemostatic parameters and glucose-lowering therapies by multivariate linear regression analysis, HOMA-IR (β = -0.185, t = -5.960, P < 0.001) and ISIMatsuda (β = 0.197, t = 6.632, P < 0.001) remained independently associated with the serum AT3 activity in patients with T2D, respectively.

CONCLUSIONS

Reduced basal and systemic insulin sensitivity are associated with decreased serum AT3 activity in patients with T2D.

The interrelationship between pregnancy, venous thromboembolism, and thyroid disease: a hypothesis-generating review

Pregnancy induces physiological changes that affect the risk of thrombosis and thyroid disease. In this hypothesis-generating review, the physiological changes in the coagulation system and in thyroid function during a normal pregnancy are described, and the incidence of venous thromboembolism (VTE) and thyroid disease in and after a pregnancy are compared and discussed. Furthermore, evidence regarding the association between thyroid disease and VTE in non-pregnant individuals is scrutinized. In conclusion, a normal pregnancy entails hormonal changes, which influence the onset of VTE and thyroid disease. Current evidence suggests an association between thyroid disease and VTE in non-pregnant individuals. This review proposes the hypothesis that maternal thyroid disease associates with VTE in pregnant women and call for future research studies on this subject. If an association exists in pregnant women specifically, such findings may have clinical implications regarding strategies for thyroid function testing and potential thromboprophylaxis in selected individuals.

Influence of high-dose antithrombin on platelet function and blood coagulation

Aim

In healthy adults, there are sufficient amounts of antithrombin in the blood to regulate thrombin. However, the effects of high concentrations of antithrombin on dose‐dependent anticoagulation and platelet function have not been reported. In this study, we assessed platelet function and blood coagulation following high‐dose antithrombin supplementation in vitro.

Methods

Blood samples were collected from 10 healthy volunteers, and samples with different antithrombin concentrations were prepared by adding an antithrombin agent (Neuart). Blood coagulation was assessed by the Thrombus‐Formation Analysis System (T‐TAS) and Rotational Thromboelastometry (ROTEM) using whole blood samples.

Results

The data obtained by the platelet chip, exclusively representing platelet function, revealed that the onset of thrombus formation was significantly delayed in a dose‐dependent manner (100%–200%, P = 0.021; 100%–500%, P = 0.011; 200%–500%, P = 0.047). In measurements using the atheroma chip, which enables assessment of blood coagulation, the thrombus formation ability was found to be reduced (100%–200%, P = 0.022; 100%–500%, P = 0.05). In the ROTEM measurements, clotting time was prolonged in a dose‐dependent manner (100%–200%: P = 0.203, 200%–500%: P = 0.005, 500%–1000%: P = 0.022), except when comparing with 100% and 200%. Although antithrombin is reportedly saturated in healthy blood, its anticoagulant ability appears to be enhanced depending on its concentration. Furthermore, data obtained from the platelet chip showed that antithrombin might reduce platelet function.

Conclusions

Antithrombin suppressed platelet function and blood coagulation in a dose‐dependent manner.

Intraoperative Hypotension in a Patient with Antithrombin Deficiency, Bilateral Pulmonary Emboli, and Cefazolin Allergy

In medicine, the search for a clear answer can at times be elusive. However, this does not necessarily preclude the administration of intelligent and thoughtful therapeutic treatments. Here, we describe a complicated emergent event of severe hypotension and near-arrest that occurred in the operating room in a young, healthy woman undergoing outpatient thyroid surgery. We detail the situation as it presented in the operating room and the measures taken to rule out potential life-threatening diagnoses and develop a thoughtful treatment plan. We further describe the evidence for and against the two remaining diagnostic possibilities: anaphylaxis versus acute pulmonary embolism.

A novel mutation of SERPINC1 in a patient presenting as recurrent cerebral sinus venous and portal vein thrombosis

: Inherited antithrombin deficiency (OMIM 107300) is a rare autosomal dominant disorder that could increase the risk of venous thromboembolism and is usually caused by mutations of SERPINC1. Herein, we present a case of a novel mutation in the SERPINC1 gene in a Chinese patient. The patient was a 54-year-old man who presented with recurrent venous thromboembolism and was without a recent history of any precipitating factors. Whole exome sequencing and Sanger sequencing identified a novel heterozygous variant on exon 2 of SERPINC1 gene (c.142G>A, p.P48S).

Antithrombin Deficiency in Trauma and Surgical Critical Care

Antithrombin deficiency (ATD) was described in 1965 by Olav Egeberg as the first known inherited form of thrombophilia. Today, it is understood that ATDs can be congenital or acquired, leading to qualitative, quantitative, or mixed abnormalities in antithrombin (AT). All ATDs ultimately hinder AT's ability to serve as an endogenous anticoagulant and antiinflammatory agent. As a result, ATD patients possess higher risk for thromboembolism and can develop recurrent venous and arterial thromboses. Because heparin relies on AT to augment its physiologic function, patients with ATD often exhibit profound heparin resistance. Although rare as a genetic disorder, acquired forms of ATD are seen with surprising frequency in critically ill patients. This review discusses ATD in the context of surgical critical care with specific relevance to trauma, thermal burns, cardiothoracic surgery, and sepsis.

Congenital antithrombin deficiency in patients with splanchnic vein thrombosis

BACKGROUND AND AIMS

Splanchnic vein thromboses (SVT) are a rare condition that can be life-threatening. The most severe thrombophilia associated to SVT is antithrombin (AT) deficiency, usually caused by SERPINC1 mutations. Although transitory AT deficiencies and congenital disorders of the N-glycosylation pathways (CDG) have been recently reported as causes of AT deficiency, the current AT clinical screening still only includes anti-FXa activity. This study aims to (a) improve the detection of AT deficiency in SVT and (b) characterize the features of AT deficiency associated with SVT.

METHODS

The study was performed in 2 cohorts: (a) 89 SVT patients with different underlying etiologies but in whom AT deficiency had been ruled out by classical diagnostic methods; and (b) 271 unrelated patients with confirmed AT deficiency and venous thrombosis. AT was evaluated by functional (anti-FXa and anti-FIIa) and immunological methods (ELISA, crossed immunoelectrophoresis, western blot), and SERPINC1 sequencing was performed.

RESULTS

In 4/89 patients (4.5%) additional alterations in AT were found (two had SERPINC1 mutations, one had a specific variant causing transient AT deficiency and one patient had CDG). In 11 of the 271 patients (4.1%) with AT deficiency and thrombosis, thrombosis was located at the splanchnic venous territory.

CONCLUSIONS

Antithrombin deficiency may be underdiagnosed by current clinical screening techniques. Therefore, a comprehensive AT evaluation should be considered in cases of rethrombosis or doubtful interpretation of anti-FXa activity levels. SVT is a relatively common localization of the thrombotic event in patients with congenital AT deficiency.