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.

Clinical Phenotype and Genetic Analysis of a Family with Hereditary Antithrombin Deficiency Caused by SERPINC1 Gene Mutation

Inherited deficiency of the antithrombin (hereditary antithrombin deficiency, AT deficiency, OMIM #613118) is a relatively rare (1:2,000-3,000) autosomal-dominant disorder with high risk of venous thromboembolism. The molecular basis of this condition has not yet fully understood, highlighting the need for further research to elucidate the underlying pathological mechanisms.This study aimed to investigate coagulation parameters and genetic phenotypes in a proband with hereditary antithrombin deficiency and her family members. Additionally, the investigation sought to provide preliminary insights for the molecular pathogenesis of this condition.Blood coagulation parameters, including plasma antithrombin activity (AT:A), antithrombin antigen (AT:Ag), protein C activity (PC:A), and protein S activity (PS:A) were measured in the peripheral blood of each family member by a Stago instrument. Peripheral blood was also extracted and sequenced to identify possible genetic mutation sites. The functional impact of variants on protein was subsequently analyzed by bioinformatics software.The proband, her mother, and brother all exhibited decreased activity and antigen of AT but normal PC and PS activity. The proband's father had normal activity and antigen levels of AT, PC, and PS. Sequencing revealed the proband's mother inherited the SERPINC1:c.661T > C,p.(Trp221Arg) heterozygous variant and her father harbored PROC:c.572_574del,p.(Lys193del) heterozygous variant while the proband as well as her brother carried both. Conservation analysis revealed that Trp221 is highly conserved across homologous species. Bioinformatics tools consistently classify the p.Trp221Arg mutation as "pathogenic" or "deleterious." Protein modeling indicated that the p.Trp221Arg variant does not alter the protein structure but may modify glycosylation sites to affect its function.The proband and family members exhibited varying degrees of decreased levels of AT and thrombosis, which were closely associated with inheritance of SERPINC1:c.661T > C,p.(Trp221Arg).

Thrombotic Diathesis Combined With Connective Tissue Disease in a Chinese Teenage Male: A Case Report

Thrombophilia is a pathological condition characterized by an increased propensity for blood clot formation and thromboembolism, resulting from various genetic or acquired factors. It can be classified as hereditary or acquired based on its etiology. Autoimmune diseases are common contributors to acquired thrombophilia. This article presents the clinical diagnosis and treatment of a patient with hereditary thrombophilia complicated by connective tissue disease, aiming to provide a reference for the clinical management of thrombophilia. A case of a 13-year-old male presenting with persistent pain and swelling in the left lower limb was investigated. Physical examination revealed there was swelling in the left lower limb with slightly elevated skin tension and warmth. Lower Limb Ultrasound: Thrombosis in the left calf muscle venous system. D-dimer was elevated and antinuclear antibodies (ANA) and titers were Positive. Family history revealed several kinsfolk had thromboembolic diseases. The patient underwent hydroxychloroquine sulfate, warfarin sodium, and aspirin for maintenance therapy. 10 months later, the patient presented with deep vein thrombosis in the left sole again. Thrombosis is a multifactorial process, and patients may have multiple thrombophilic risk factors simultaneously. Etiological screening for thrombophilia should not focus solely on a single risk factor. If autoimmune diseases cannot fully explain the severity of thrombophilia, other risk factors should be further investigated. It is essential to appropriately determine the indications for genetic screening in patients with VTE and autoimmune diseases.

Bilateral adrenal hemorrhage in a postpartum woman with multiple thromboemboli: A case report

BACKGROUND

Bilateral adrenal hemorrhage is a rare but often a fatal cause of primary adrenal insufficiency that can result in adrenal crisis if not identified and managed appropriately.

CASE PRESENTATION

We present a case of a 27-year-old Caucasian female who was admitted to the hospital 17 days postpartum with pleuritic chest and flank pain, shortness of breath and nausea. Computed tomography imaging confirmed multiple thromboemboli including pulmonary emboli and noted bilateral bulky adrenal glands. She was managed for infection and pulmonary emboli; however, she complained of persistent headaches, nausea, and vomiting despite appropriate management. Radiology re-review found the computed tomography imaging was consistent with bilateral adrenal hemorrhage in hindsight. Subsequent endocrine evaluation with hypothalamic-pituitary-adrenal axis interrogation and adrenocorticotropic hormone (Synacthen) stimulation testing confirmed resultant primary adrenal insufficiency. She required urgent intravenous hydrocortisone and was subsequently discharged on oral adrenal replacement therapy and anticoagulation.

CONCLUSIONS

Delay in identification and treatment of adrenal insufficiency can lead to catastrophic outcomes. This case highlights the challenge of diagnosing bilateral adrenal hemorrhage and resultant adrenal insufficiency as patients may not present with the classic risk factors, signs, symptoms, and electrolyte derangements.

Antithrombin Deficiency and Thrombosis: A Wide Clinical Scenario Reported in a Single Institution

Congenital antithrombin (AT) deficiency represents the form of thrombophilia with the highest thrombotic risk. It is characterized by a heterogeneous clinical presentation, depending mostly on the family history of thrombosis and type of genetic mutation. Inherited AT deficiency promotes idiopathic thrombosis at an early age (even in the pediatric population) and at atypical sites. Therefore, a positive family background necessitates ruling out this high-risk thrombophilia at a young age. Studying first-degree relatives, even if they are asymptomatic, is essential to establish thromboprophylaxis and a proper therapeutic approach in case of thrombosis. Patients with congenital AT deficiency require indefinite anticoagulation owing to the high thrombotic recurrence rate. Here, we present four unrelated cases reported in our institution who were diagnosed with hereditary AT deficiency, with a contrasting clinical evolution.

Hydration Status of Geriatric Patients Is Associated with Changes in Plasma Proteome, Especially in Proteins Involved in Coagulation

Due to multifactorial reasons, such as decreased thirst and decreased total body water, elderly patients are vulnerable to dehydration. The study aims to investigate whether moderate dehydration or hyperhydration affects the blood proteome. Blood samples, medication, and bioelectrical impedance analysis (BIA) details were collected from 131 geriatric patients (77 women and 54 men aged 81.1 ± 7.2 years). Based on an evaluation by Bioelectrical Impedance Vector Analyses (BIVAs) of this cohort, for each hydration status (dehydrated, hyperhydrated, and control), five appropriate blood plasma samples for both males and females were analyzed by liquid chromatography-mass spectrometry (LC-MS). Overall, 262 proteins for female patients and 293 proteins for male patients could be quantified. A total of 38 proteins had significantly different abundance, showing that hydration status does indeed affect the plasma proteome. Protein enrichment analysis of the affected proteins revealed "Wound Healing" and "Keratinization" as the two main biological processes being dysregulated. Proteins involved in clot formation are especially affected by hydration status.

Antithrombin diagnostics by mass spectrometry: Development and analytical validation of a next-generation test

Background

Antithrombin deficiency is a rare but severe disorder leading to high risk of thrombosis. The current clinical care pathway relies on activity tests, which only provide overall functional information on the in vitro activity of antithrombin. However, antithrombin exists in many different forms, also known as proteoforms, with varying clinical phenotypes. Precision diagnostics, facilitated by mass spectrometry, provides a strategy to improve patient diagnostics by molecular characterization.

Objectives

To develop and analytically validate a mass spectrometry-based test for molecular characterization of antithrombin.

Methods

The test was analytically validated based on predefined analytical performance specifications. The validation covered imprecision, carryover, linearity, stability, analytical specificity, a provisional reference interval, and an explorative method comparison.

Results

The test passed the predefined analytical performance specifications with a mean within-laboratory imprecision of 5.9%, linearity between 0.08 and 2.58 μmol/L, and a provisional reference interval of 1.07 to 1.49 μmol/L. When measuring samples with a suspected quantitative deficiency, the test showed a good correlation with a commercial activity test (Pearson r = 0.88).

Conclusion

The test passed the validation, and we now envision the use of the test for exploration of the clinical relevance of specific antithrombin proteoforms. Puzzling cases of antithrombin deficiency, for instance, due to ambiguous activity results or an atypical clinical presentation, can be investigated by the LC-MRM mass spectrometry test serving as an add-on to the activity test and providing a molecular diagnosis. Clinical studies are planned to investigate the potential of the test to improve antithrombin diagnostics. Furthermore, the molecular information gained using the test may aid in establishing better risk stratification and a basis for personalized medicine.

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.

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.

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.

Evolving Knowledge on Primary and Secondary Prevention of Venous Thromboembolism in Carriers of Hereditary Thrombophilia: A Narrative Review

The association between heritability of venous thromboembolism (VTE) and thrombophilia was first reported clinically in 1956, later followed by the first description of a congenital cause of hypercoagulability-antithrombin deficiency-in 1965. Since then, our knowledge of hereditary causes of hypercoagulability, which may predispose carriers to VTE has improved greatly. Novel genetic defects responsible for severe thrombophilia have been recently identified and we have learned that a wide range of interactions between thrombophilia and other genetic and acquired risk factors are important determinants of the overall individual risk of developing VTE. Furthermore, therapeutic strategies in thrombophilic patients have benefited significantly from the introduction of direct oral anticoagulants. The present review is an overview of the current knowledge on the mechanisms underlying inherited thrombophilia, with a particular focus on the latest achievements in anticoagulation protocols and prevention strategies for thrombosis in carriers of this prothrombotic condition.

Evolving Knowledge on Primary and Secondary Prevention of Venous Thromboembolism in Carriers of Hereditary Thrombophilia: A Narrative Review

The association between heritability of venous thromboembolism (VTE) and thrombophilia was first reported clinically in 1956, later followed by the first description of a congenital cause of hypercoagulability-antithrombin deficiency-in 1965. Since then, our knowledge of hereditary causes of hypercoagulability, which may predispose carriers to VTE has improved greatly. Novel genetic defects responsible for severe thrombophilia have been recently identified and we have learned that a wide range of interactions between thrombophilia and other genetic and acquired risk factors are important determinants of the overall individual risk of developing VTE. Furthermore, therapeutic strategies in thrombophilic patients have benefited significantly from the introduction of direct oral anticoagulants. The present review is an overview of the current knowledge on the mechanisms underlying inherited thrombophilia, with a particular focus on the latest achievements in anticoagulation protocols and prevention strategies for thrombosis in carriers of this prothrombotic condition.

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.

Semi-empirical anticoagulation model (SAM): INR monitoring during Warfarin therapy

The International Normalized Ratio (INR) monitoring is an essential component to manage thrombotic disease therapy. This study presents a semi-empirical model of INR as a function of time and assigned therapy (Warfarin, k-vitamin). With respect to other methodologies, this model is able to describe the INR using a limited number of parameters and is able to describe the time variation of INR described in the literature. The presented methodology showed great accuracy in model calibration [(trueness (precision)]: 0.2% (0.1%) to 1.2% (0.3%) for coagulation factors, from 5% (9%) to 9.7% (12%) for Warfarin-related parameters and 38% (40%) for K-vitamin-related parameters. The latter value was considered acceptable given the assumptions made in the model. It has two other important results: the first is that it was able to correctly estimate INR with respect to daily therapy doses taken from the literature. The second is that it introduces a single numeric semi-empirical parameter that is able to correlate INR/dose response to physiological and environmental condition of patients.

Maxillofacial and oral surgery in patients with thrombophilia: safe territory for the oral surgeon? A single-center retrospective study

OBJECTIVE

The aim of this study was to analyze patients with thrombophilia who underwent oral and/or maxillofacial surgery at our center.

STUDY DESIGN

We performed a retrospective analysis of patients with hereditary or acquired thrombophilia who had undergone oral/maxillofacial surgery between January 1, 2000 and December 31, 2019. Data regarding demographic and patient characteristics, surgical treatment modalities, antithrombotic therapies, and complications were analyzed.

RESULTS

A total of 76 eligible patients (26 male, 50 female) were included in this study, with a mean follow-up period of 3.8 months (range, 0-51 months). The mean age at time of surgery was 44.7 ± 19.4 years. Seven different hereditary and acquired thrombophilia were identified: factor V Leiden (n = 31; 40.8%), prothrombin G20210A mutation (n = 5; 6.6%), protein C deficiency (n = 4; 5.3%), protein S deficiency (n = 11; 14.5%), antiphospholipid syndrome (n = 10; 13.2%), hyperhomocysteinemia (n = 8; 10.5%), and elevated factor VIII (n = 2; 2.6%). Complications occurred in 9 patients (11.8%) and included postoperative infections (n = 6; 7.9%) and postoperative bleeding (n = 3; 3.9%).

CONCLUSION

Our data suggest that oral and/or maxillofacial surgery in patients with a confirmed diagnosis of thrombophilia is not associated with a burden of thrombosis or high complication rates. Furthermore, we formulated a guideline for preoperative antithrombotic therapy for patients with thrombophilia undergoing oral and/or maxillofacial surgery.

Functional Characterization of Antithrombin Mutations by Monitoring of Thrombin Inhibition Kinetics

Inactivation of thrombin by the endogenous inhibitor antithrombin (AT) is a central mechanism in the regulation of hemostasis. This makes hereditary AT deficiency, which is caused by SERPINC1 gene mutations, a major thrombophilic risk factor. Aim of this study was to assess to what extent AT mutations impair thrombin inhibition kinetics. The study population included 36 thrombophilic patients with 19 different mutations and mean AT levels of 65% in a thrombin-based functional assay, and 26 healthy controls. To assess thrombin inhibition kinetics, thrombin (3.94 mU/mL final concentration) was added to citrated plasma. Subsequently, endogenous thrombin inhibition was stopped by addition of the reversible thrombin inhibitor argatroban and the amount of argatroban-complexed thrombin quantified using an oligonucleotide-based enzyme capture assay. The plasma half-life of human thrombin was significantly longer in patients with AT mutations than in the controls (119.9 versus 55.9 s). Moreover, it was disproportionately prolonged when compared with preparations of wild type AT in plasma, in whom a comparable thrombin half-life of 120.8 s was reached at a distinctly lower AT level of 20%. These findings may help to better understand the increased thrombotic risk of SERPINC1 mutations with near normal AT plasma levels in functional assays.

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).

Successful treatment of a massive sinus thrombosis in a Chinese woman with antithrombin III deficiency: a case report and review of the literature

: The incidence of antithrombin III (AT III) deficiency is very rare. The most common complication of AT III deficiency is deep venous thrombosis, which causes a low incidence of intracranial sinus thrombosis. We presented a 31-year-old Chinese woman patient who had a family history of AT III deficiency admitted to our hospital. She had a history of pulmonary embolism. She took rivaroxaban for a long time to prevent thrombosis. After giving birth, she stopped taking the medication for half a year and suffered from drug withdrawal symptoms. Four months after drug withdrawal, she suddenly fell into a coma. After diagnosis, it was found to be caused by a subarachnoid hemorrhage. Finally, she was diagnosed with sagittal and transverse sinus thrombosis. After treatment with mechanical thrombectomy, she fully recovered. In sum, we concluded that mechanical thrombectomy was efficient for AT III deficiency and treating thrombosis.

Prevention of Venous Thromboembolism during Pregnancy and the Puerperium with a Special Focus on Women with Hereditary Thrombophilia or Prior VTE-Position Paper of the Working Group in Women's Health of the Society of Thrombosis and Haemostasis (GTH)

Venous thromboembolism (VTE) is a major cause of maternal morbidity during pregnancy and the postpartum period. Because there is a lack of adequate study data, management strategies for the prevention of VTE during pregnancy have mainly been deduced from case-control and observational studies and extrapolated from recommendations for non-pregnant patients. The decision for or against pharmacologic thromboprophylaxis must be made on an individual basis weighing the risk of VTE against the risk of adverse side effects such as severe bleeding complications. A comprehensive, multidisciplinary approach is often essential as the clinical scenario is made more complex by the specific obstetric context, especially in the peripartum period. As members of the Working Group in Women's Health of the Society of Thrombosis and Haemostasis (GTH), we summarize the evidence from the available literature and aim to establish a more uniform strategy for VTE risk assessment and thromboprophylaxis in pregnancy and the puerperium. In this document, we focus on women with hereditary thrombophilia, prior VTE and the use of anticoagulants that can safely be applied during pregnancy and the lactation period.

Phenotypic and Genotypic Analysis of a Hereditary Antithrombin Deficiency Pedigree Due to a Novel SERPINC1 Mutation (p.Met281Thr)

Antithrombin (AT) is one of the physiological anticoagulants that are mainly synthesized in the liver. As a protease inhibitor belonging to the serpin superfamily, AT is able to inactivate thrombin and inhibit activated coagulation factors IX, X, XI, and XII (FIXa, FXa, FXIa, and FXIIa).1 Moreover, it has been found that AT can inhibit activated FVII (FVIIa) by accelerating dissociation of FVIIa-tissue factor complex and preventing it from recombining.2 The AT gene (SERPINC1), located on chromosome 1 at q23.1-23.9 and spreads 13.5 kb, is composed of seven extrons and six introns.3 Hereditary AT deficiency is a rare thrombotic disorder caused by defects in SERPINC1 gene.4 It is inherited in an autosomal-dominant manner with an incidence of roughly 0.02 to 0.25% in the general population and 2 to 5% in patients with a history of venous thromboembolism (VTE).1 5 The most common thrombotic manifestations of patients with AT deficiency are VTEs, and their risks of VTE are approximately 20 times higher than those of nondeficient individuals.6 And the consequences of thrombophilia caused by AT deficiency are more severe than those of protein C and S protein deficiency,2 so it should be given sufficient attention.

How I treat patients with hereditary antithrombin deficiency

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

The prevention and management of asparaginase-related venous thromboembolism in adults: Guidance from the SSC on Hemostasis and Malignancy of the ISTH

Venous thromboembolism is a common complication of asparaginase-based chemotherapy regimens for the treatment of acute lymphoblastic leukemia. Thrombosis associated with asparaginase administration poses a number of specific and often clinically challenging management decisions. This review provides guidance on the prevention and treatment of thrombosis associated with asparaginase in adults including discussions on antithrombin repletion, pharmacologic thromboprophylaxis, cerebral venous thrombosis, and therapeutic anticoagulation.

Superior mesenteric venous thrombosis as a first manifestation of Antithrombin III deficiency in the postoperative course of laparoscopic sleeve gastrectomy: a case study of 2 patients from 1211 bariatric patients

Superior mesenteric venous thrombosis (SMVT) following laparoscopic sleeve gastrectomy (LSG) is a rare, potentially life-threatening complication, which presents either isolated, or as a part of portal/mesenteric/splenic vein thrombosis. Distinction between them possibly confers an important clinical and prognostic value. Antithrombin III (ATIII) deficiency causes an hypercoagulable state which predisposes to SMVT. We report the clinical presentation and treatment of two patients among 1211 LSGs (incidence = 0.165%) that presented with isolated SMVT and ATIII deficiency in an Academic Bariatric Center. Both patients had an unremarkable past medical history; none was smoker or had a previously known thrombophillic condition/thrombotic episode. Mean time of presentation was 15.5 days after LSG. Despite aggressive resuscitative and anticoagulation measures, surgical intervention was deemed necessary. No mortalities were encountered. Coagulation tests revealed ATIII deficiency in both patients.

Genetic aetiology of early infant deaths in a neonatal intensive care unit

BACKGROUND

Congenital anomalies are the leading cause of early neonatal death in neonatal intensive care units (NICUs), but the genetic causes are unclear. This study aims to investigate the genetic causes of infant deaths in a NICU in China.

METHODS

Newborns who died in the hospital or died within 1 week of discharge were enrolled from Children's Hospital of Fudan University between January 1, 2015 and December 31, 2017. Whole exome sequencing was performed in all patients after death.

RESULTS

There were 223 deceased newborns with a median age at death of 13 days. In total, 44 (19.7%) infants were identified with a genetic finding, including 40 with single nucleotide variants (SNVs), two with CNVs and two with both SNVs and CNVs. Thirteen (31%, 13/42) patients with SNVs had medically actionable disorders based on genetic diagnosis, which included 10 genes. Multiple congenital malformation was identified as the leading genetic cause of death in NICUs with 13 newborns identified with variants in genes related to multiple congenital malformations. For newborns who died on the first day, the most common genetic cause of death was major heart defects, while metabolic disorders and respiratory failure were more common for newborns who died in the first 2 weeks.

CONCLUSION

Our study shows genetic findings among early infant deaths in NICUs and provides critical genetic information for precise genetic counselling for the families. Effective therapies enable the improvement of more than a quarter of newborns with molecular diagnoses if diagnosed in time.

Antithrombin concentrate during pregnancy in congenital antithrombin deficiency: a single-center experience

: Pregnancy carries a high risk of thromboembolic complications, especially in the postpartum period. This risk is particularly high in women with inherited thrombophilias, among these antithrombin deficiency seems to carry the highest risk. In this case, the use of low molecular weight heparin (LMWH) is recommended, while the use of antithrombin concentrate is controversial. We report our experience of seven pregnancies occurred in five women: two, with a personal and familiar history negative for venous thromboembolism, were treated with LMWH during pregnancy and antithrombin concentrate immediately before and after the delivery. The other three women had a personal and familiar history positive for venous thromboembolism and were treated with LMWH and antithrombin concentrate during all the pregnancy and the postpartum period. No thromboembolic or hemorrhagic complications were observed in both groups, demonstrating that our strategy could be safe and effective.

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.

Thrombophilia, risk factors and prevention

INTRODUCTION

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

Revisiting antithrombin in health and disease, congenital deficiencies and genetic variants, and laboratory studies on α and β forms

Antithrombin [AT] is the main inhibitor for activated plasma coagulation serine esterases, inhibiting thrombin, Factors Xa and IXa, but also Factors XIIa, XIa, VIIa, kallicrein, and plasmin. Its activity is highly enhanced by heparin, through binding to the pentasaccharide sequences, for inhibition of all coagulation proteases, except thrombin, which inhibition requires its additional binding to the heparin polysaccharide chain. However, AT is the major inhibitor of thrombin in the blood circulation. Congenital or acquired deficiencies of AT expose affected patients to an increased risk of developing unprovoked and recurrent thrombo-embolic diseases. Antithrombin can be measured with various laboratory techniques, by either immunological or functional methods. Earlier, a radial immunodiffusion immunoassay allowed measurement of the protein antigenic content. Functional assays are mainly designed with Anti-Thrombin or Anti-Factor Xa chromogenic methods and are useful for detecting genetic molecular mutations with decreased inhibitory activity and contributed to study the conformational changes of antithrombin and its variants, which potentially regulate the activity of this serine protease inhibitor. These assays are not equivalent in terms of diagnosing protein abnormalities, associated with increased thrombotic incidence, and they have variable performance for reflecting impaired antithrombin binding capacity for heparin, reduced progressive inhibition of serine proteases, or accelerated switch rates to the latent and less active forms. A small proportion of AT (<10%) is present in blood in the β-form, with a lower oligosaccharide content, a lower Molecular Weight, a higher binding rate to endothelial glycosaminoglycans, and a higher anticoagulant activity, hence requiring specific laboratory methods for its measurement. The β-AT form is then of critical importance for controlling blood activation by tissue injury and preventing development of thrombo-embolic diseases. This article reviews the performance characteristics of the currently available assays, and their usefulness for monitoring the use of AT concentrates in intensive care units, disseminated intravascular coagulation or severe infections, to restore the anticoagulant protective effect of heparin by supplementing the requested AT concentration. The issues of automation, harmonization and standardization are also revisited and discussed.