Inherited Antithrombin Deficiency Research Articles

A retrospective study of the management and outcomes of pregnancies with inherited antithrombin deficiency.

Antithrombin (AT) deficiency is a rare but highly thrombogenic inherited thrombophilia. Its association with adverse pregnancy outcomes (APO) is undefined. There is limited guidance on managing AT deficiency in pregnancy. Some significant issues remain controversial, including risk assessment for prophylactic anticoagulation, anticoagulant therapy, and monitoring. Our goal was to examine if the antepartum management of patients with AT deficiency affected their pregnancy outcomes. This retrospective, single-center observational study included pregnant women with inherited AT deficiency in Peking Union Medical College Hospital between 2013 and 2024. Seventeen pregnancies in 6 women with AT deficiency were identified. A total of 7 pregnancies received adjusted-dose low-molecular-weight heparin (LMWH) and were monitored by anti-Xa level, AT activity, and D-dimer. There were 5 live births (all received LMWH), 7 second-trimester abortions (1 received LMWH), and 5 early pregnancy losses (1 received LMWH). There were 5 abruptio placentae events (3 received LMWH) and 7 thrombotic events (2 received LMWH). AT deficiency is at least an important partial factor contributing to APO. It is suggested to make a full assessment of AT patients both for venous thrombus embolism and APO risk. We observed a high prevalence of heparin resistance and a positive correlation between adequate anticoagulation and pregnancy outcome based on tight monitoring with anti-Xa level and timely adjustment of the LMWH dosage.

PB1081 Identification of Related Molecular Biological Effects on Two Novel Point Mutations in Inherited Antithrombin Deficiency

PB1081 Identification of Related Molecular Biological Effects on Two Novel Point Mutations in Inherited Antithrombin Deficiency

PB0544 Management of Inherited Antithrombin Deficiency in Pregnancy and Puerperium: Single Center Experience

PB0544 Management of Inherited Antithrombin Deficiency in Pregnancy and Puerperium: Single Center Experience

Analysis of phenotype and gene mutation in three pedigrees with inherited antithrombin deficiency.

Inherited AT deficiency is an autosomal-dominant thrombophilic disorder usually caused by various SERPINC1 defects associated with a high risk of recurrent venous thromboembolism. In this article, the phenotype, gene mutation, and molecular pathogenic mechanisms were determined in three pedigrees with inherited AT deficiency. Coagulation indices were examined on STAGO STA-R-MAX analyzer. The AT:Ag was analyzed by ELISA. All exons and flanking sequences of SERPINC1 were amplified by PCR. AT wild type and three mutant expression plasmids were constructed and then transfected into HEK293FT cells. The expression level of AT protein was analyzed by ELISA and Western blot. The AT:A and AT:Ag of probands 1 and 3 were decreased to 49% and 52 mg/dL, 38% and 44 mg/dL, respectively. The AT:A of proband 2 was decreased to 32%. The SERPINC1 gene analysis indicated that there was a p.Ile421Thr in proband 1, a p.Leu417Gln in proband 2, and a p.Met252Thr in proband 3, respectively. The AT mRNA expression level of the three mutants was not significantly different from AT-WT by qRT-PCR. The results of ELISA and Western blot tests showed that the AT-M252T and AT-I421T mutants had a higher AT expression than the AT wild type (AT-WT), and the AT protein expression of AT-L417Q mutants had no significant difference compared with AT-WT in the cell lysate. The AT expression levels of AT-M252T and AT-I421T mutants were lower than that of AT-WT, and there was no significant difference between AT-L417Q mutant and AT-WT in the supernatant. The p.I421T and p.M252T mutations affected the secretion of AT protein leading to type I AT deficiency of probands 1 and 3. The p.Leu417Gln mutation was responsible for the impaired or ineffective activity AT protein in proband 2 and caused type II AT deficiency.

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.

Molecular Dissection of Structural Variations Involved in Antithrombin Deficiency

Inherited antithrombin deficiency, the most severe form of thrombophilia, is predominantly caused by variants in SERPINC1. Few causal structural variants have been described, usually detected by multiplex ligation-dependent probe amplification or cytogenetic arrays, which only define the gain or loss and the approximate size and location. This study has done a complete dissection of the structural variants affecting SERPINC1 of 39 unrelated patients with antithrombin deficiency using multiplex ligation-dependent probe amplification, comparative genome hybridization array, long-range PCR, and whole genome nanopore sequencing. Structural variants, in all cases only affecting one allele, were deleterious and caused a severe type I deficiency. Most defects were deletions affecting exons of SERPINC1 (82.1%), but the whole cohort was heterogeneous, as tandem duplications, deletion of introns, or retrotransposon insertions were also detected. Their size was also variable, ranging from 193 bp to 8 Mb, and in 54% of the cases involved neighboring genes. All but two structural variants had repetitive elements and/or microhomologies in their breakpoints, suggesting a common mechanism of formation. This study also suggested regions recurrently involved in structural variants causing antithrombin deficiency and found three structural variants with a founder effect: the insertion of a retrotransposon, duplication of exon 6, and a 20-gene deletion. Finally, nanopore sequencing was determined to be the most appropriate method to identify and characterize all structural variants at nucleotide level, independently of their size or type.

Inherited antithrombin deficiency in pregnancy

Inherited AntiThrombin Deficiency (ATD) is a rare and high-risk thrombophilia. It is associated with a high risk of venous thromboembolism, thrombosis, and the risk is escalated further in the prothrombotic state of pregnancy. Due to the thrombotic tendency it is also associated with placental dysfunction due to placental thrombosis. Untreated mothers with ATD have increased rates of second and third trimester loss, pre-eclampsia & eclampsia, placental abruption, and intra-uterine growth restriction resulting in small for gestational age babies.We have conducted a comprehensive review of the literature and guidelines & summarise the role of antithrombin, how to test for it, the evidence for its role in thrombosis and obstetric complications and how best to manage this. We also aim to present what we believe is best practise for managing ATD during pregnancy and therefore provide a much needed practical guide.Managing these women during pregnancy is designed to reduce their risk of thrombosis and late obstetric complications. Due to the rarity of the condition and the ethical difficulties surrounding clinical trials in pregnant women no randomised controlled trials or large observational studies have been conducted in this area; evidence is limited to small cohort studies, which are usually retrospective. Definitions such as ‘miscarriage’ and ‘fetal loss’ are also discordant between studies and associations which makes data comparison difficult. Thus there is limited guidance on the management of ATD in pregnancy. We recommend the use of low molecular weight heparin (LMWH) during pregnancy with regular anti- Xa monitoring to ensure that women receive adequate antithrombotic therapy. Due to the efficacy of LMWH working through potentiation of antithrombin, in those with ATD, high levels of LMWH are usually required. We discuss the use of antithrombin concentrates at times where the use of LMWH is contraindicated, such as during delivery.Emerging evidence suggests that the type of antithrombin deficiency is important in risk stratification along with the individual's own thrombotic risk factors, thrombosis history and family history.

Novel Mutation p.Asp374Val of SERPINC1 in a Turkish Family with Inherited Antithrombin Deficiency

Novel Mutation p.Asp374Val of SERPINC1 in a Turkish Family with Inherited Antithrombin Deficiency

Тромботические события при редких формах генетических тромбофилий

Цель исследования: изучить лабораторный фенотип редких мутаций Лейдена [FVL А(1961)A] и гена протромбина [FII А(20210)A] при их клинической реализации в виде тромбозов. Материалы и методы. Проведено многоцентровое проспективное наблюдательное исследование, включающее 80 носителей редких генетических форм тромбофилий: FVL А(1961)A (n = 31), FII А(20210)A (n = 10) и компаунд FII G(20210)A + FVL G(1691)A (n = 39). У всех пациентов исследована резистентность фактора Va к активированному протеину С (APC-R) по нормализованному отношению (НО) и уровень активности протромбина в плазме крови в состоянии физического здоровья и в случае эпизода тромботического события. Результаты. Определена ассоциативная связь развития тромботических событий со снижением НО при оценке APC-R как у гомозиготных носителей мутации Лейден (Ме = 0,35; 95% ДИ = 0,31–0,37 по НО), так и гетерозиготных компаундов (Ме = 0,43; 95% ДИ = 0,42–0,45 по НО). Заключение. Лабораторный мониторинг пациентов с редкими формами генетических тромбофилий позволяет выделить группу высокого тромбогенного риска, нуждающуюся в пролонгированной тромбопрофилактике. Objectives: to study the laboratory phenotype of rare Leiden mutation [FVL A(1961)A] and the prothrombin gene mutation [FII А(20210)A] implementating clinically as thrombosis. Patients / Methods. A multicenter prospective observational study included 80 carriers of rare genetic kinds of thrombophilia: FVL A(1961)A (n = 31), prothrombin FII А(20210)A (n = 10) and the compound FII G(20210)A + FVL G(1691)A (n = 39). All patients were tested for the factor Va resistance to activated protein C (APC-R), normalized ratio (NR), and the plasma prothrombin activity (%) in healthy conditions and in the case of thrombotic event. Results. An associative relation between the development of thrombotic events and a decrease in NR was determined when assessing APC-R, both in homozygous carriers of the Leiden mutation (Me = 0.35; 95% CI = 0.31–0.37 in NR) and heterozygous compounds (Me = 0.43; 95% СI = 0.42–0.45 in NR). Conclusions. Laboratory follow up for patients with rare kinds of genetic thrombophilias allows to identify a group at high thrombogenic risk requiring prolonged thromboprophylaxis.

Management and outcomes of newborns at risk for inherited antithrombin deficiency

BackgroundAs levels of antithrombin (AT) are low at birth, diagnosing inherited AT deficiency in newborns is challenging. In Stockholm, Sweden, pregnant women with known AT deficiency are referred to the Karolinska University Hospital, where local guidelines for management of newborns at risk of inherited AT deficiency have been established. Data on pregnancy, obstetric, and neonatal outcomes are recorded in a registry. ObjectivesWe aimed to evaluate the current practice at the Karolinska University Hospital for managing delivery of newborns at risk for AT deficiency, the predictive value of AT levels at birth, and the neonatal outcomes of newborns with AT deficiency. Patients/MethodsThis was an observational, retrospective study. All children born to mothers with AT deficiency at the Karolinska University Hospital 2003‐2018 were identified from the registry and included in the study. Data were collected from the medical records and the registry. AT activity was measured postnatally and after 6 months of age. ResultsThe total study cohort included 41 newborns. There was a significant association between low AT values postnatally and after 6 months of age (P = .001). Half (21/41) of the children were diagnosed with AT deficiency; two suffered from sinus thrombosis, which presented at 10 days of age. Both children with sinus thrombosis were delivered using vacuum extraction. ConclusionsThe current practice of testing newborns can in most cases predict inherited AT deficiency. The risk for thrombosis during the neonatal period is enhanced by the use of instrumental delivery.

Antithrombin p.Thr147Ala: The First Founder Mutation in People of African Origin Responsible for Inherited Antithrombin Deficiency.

Hereditary antithrombin deficiency is a rare autosomal-dominant disorder predisposing to recurrent venous thromboembolism (VTE). To date, only two founder mutations have been described. We investigated the antithrombin p.Thr147Ala variant, found in 12 patients of African origin. This variant is known as rs2227606 with minor allele frequency of 0.5% in Africans and absent in Europeans. A possible founder effect was investigated. Phenotypical characterization was established through immunological and functional methods, both under basal and stress conditions. Recombinant antithrombin molecules were constructed by site-directed mutagenesis and expressed in HEK-293T cells. Secreted antithrombin was purified and functionally characterized. Structural modeling was performed to predict the impact of the mutation on protein structure. A novel nanopore sequencing approach was used for haplotype investigation. Ten patients experienced VTE, stroke, or obstetric complications. Antithrombin antigen levels and anti-IIa activity were normal or slightly reduced while anti-Xa activity was reduced with only one commercial assay. On crossed immunoelectrophoresis, an increase of antithrombin fractions with reduced heparin affinity was observed under high ionic strength conditions but not under physiological conditions. The recombinant p.Thr147Ala protein displayed a reduced anti-Xa activity. Structural modeling revealed that residue Thr147 forms three hydrogen bonds that are abolished when mutated to alanine. The investigated patients shared a common haplotype involving 13 SERPINC1 intragenic single nucleotide polymorphisms. Antithrombin p.Thr147Ala, responsible for antithrombin type II heparin binding site deficiency, is the first founder mutation reported in people of African ancestry. This study further emphasizes the limitations of commercial methods to diagnose this specific subtype.

Phenotypic and genetic analysis of a pedigree with inherited antithrombin deficiency

Phenotypic and genetic analysis of a pedigree with inherited antithrombin deficiency

Genotype phenotype correlation in a pediatric population with antithrombin deficiency.

Inherited antithrombin (AT) deficiency is a rare autosomal dominant disorder, caused by mutations in the AT gene (SERPINC1). Considering that the genotype phenotype relationship in AT deficiency patients remains unclear, especially in pediatric patients, the aim of our study was to evaluate genotype phenotype correlation in a Serbian pediatric population. A retrospective cohort study included 19 children younger than 18years, from 15 Serbian families, with newly diagnosed AT deficiency. In 21% of the recruited families, mutations affecting exon 4, 5, and 6 of the SERPINC1 gene that causes type I AT deficiency were detected. In the remaining families, the mutation in exon 2 causing type II HBS (AT Budapest 3) was found. Thrombosis events were observed in 1 (33%) of those with type I, 11 (85%) of those with AT Budapest 3 in the homozygous respectively, and 1(33%) in the heterozygous form. Recurrent thrombosis was observed only in AT Budapest 3 in the homozygous form, in 27% during initial treatment of the first thrombotic event. Abdominal venous thrombosis and arterial ischemic stroke, observed in almost half of the children from the group with AT Budapest 3 in the homozygous form, were unprovoked in all cases.Conclusion: Type II HBS (AT Budapest 3) in the homozygous form is a strong risk factor for arterial and venous thrombosis in pediatric patients. What is Known: • Inherited AT deficiency is a rare autosomal dominant disorder, caused by mutations in the SERPINC1gene. • The genotype phenotype correlation in AT deficiency patients remains unclear, especially in pediatric patients. What is New: • The genetic results for our paediatric population predominantly showed the presence of a single specific mutation in exon 2, that causes type II HBS deficiency (AT Budapest 3). • In this group thrombosis mostly occurred as unprovoked, in almost half of them as abdominal thrombosis or stroke with high incidence of recurrent thrombosis, in 27% during initial treatment.

Incidence and features of thrombosis in children with inherited antithrombin deficiency.

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

Association of hereditary antithrombin deficiency with intrauterine growth restriction

: Antithrombin is a major suppressor of thrombin, factor Xa and blood coagulation. Inherited antithrombin deficiency is rare and is considered among the common causes of inherited thrombophilia. The relationship between antithrombin and IUGR, is questionable. The aim of this study was to trace the relationship between antithrombin deficiency and the intrauterine weight reduction and neonatal morbidity. The study was conducted on 55 full-term neonates (including 25 baby boys and 30 baby girls), all were admitted to Neonatal Intensive Care Unit in Cairo University Hospitals with IUGR; and another 110 healthy full-term neonates as control group. ATIII activities were assessed in citrated of patient and control samples automatically on coagulometer (Stago, France). There was a highly significant relationship regarding ATIII deficiency in IUGR group in relation to control group (P value <0.001). In conclusion, we have identified antithrombin deficiency in Egyptian infants as an additional cause for low-birth weight and intrauterine growth retardation.

Pulmonary embolism presenting with acute abdominal pain in a girl with stable ankle fracture and inherited antithrombin deficiency.

Pulmonary embolism presenting with acute abdominal pain in a girl with stable ankle fracture and inherited antithrombin deficiency.

The Impact of Antithrombin Deficiency on Women's Reproductive Health Experiences and Healthcare Decision-Making.

Women with inherited antithrombin (AT) deficiency are at high risk for venous thromboembolism (VTE), especially during times of estrogen exposure, but little is known about patient-oriented reproductive decision-making in this population. Provider-administered survey of women with AT deficiency. Participants were asked to discuss their diagnosis of AT deficiency and questioned about (1) contraception, (2) pregnancies, and (3) menorrhagia, and the impact of their AT deficiency on each reproductive health experience. Of 31 women with inherited AT deficiency, 18 (58%) were surveyed, 8 (26%) were unreachable, and 5 (16%) were deceased. Twelve (67%) had a VTE, including two which occurred during pregnancy and five during oral contraceptive (OCP) use. Women reported using OCPs, intrauterine device (IUD), and condoms for contraception. Of five women diagnosed with AT deficiency while taking OCPs, three switched to an IUD, one to condoms, and one used no alternative method. Eighteen women reported 42 total pregnancies, with 33 (79%) resulting in live term birth, 3 (7%) in live preterm birth, and 6 (14%) in spontaneous abortion at a median of 12 weeks. Four (22%) women reported the use of anticoagulation during pregnancy. Eleven (61%) women reported menorrhagia and 4 (36%), while on anticoagulation for VTE events. Ten of 18 women (56%) reported that the diagnosis of AT had affected their reproductive health in some way. Women with AT deficiency require careful multidisciplinary management to avoid complications in the setting of contraception and pregnancy. AT deficiency impacts women's reproductive health experiences and patient-oriented reproductive decision-making is key.

Idiopathic thrombosis.

Idiopathic thrombosis involves a group of inherited thrombophilia predisposed to severe thrombosis of early onset and associated with an adverse outcome due to recurrence, and therefore, requires long-term anticoagulation therapy. The causative factors of a predisposition to thrombosis include immobility, dehydration, infection, surgery, injury, cancer, pregnancy, and estrogen use. The inherited deficiencies of antithrombin (AT), protein C (PC), and protein S (PS) are specified as "Specific Pediatric Chronic Diseases." However, medical expense assistance for patients terminates when they reach the age of 20 years. On April 1st 2017, "Idiopathic Thrombosis due to Inherited Thrombophilia," consisting of inherited AT, PC, and PS deficiencies, was specified as an "Intractable Disease," and aid for medical expenses became available. Accordingly, progress in the research and practice of idiopathic thrombosis is expected in future to improve the medical care system and to construct a database via clinical surveys.

Issues in the Diagnosis and Management of Hereditary Antithrombin Deficiency.

To review insights gained in the past several years about hereditary antithrombin (AT) deficiency and to outline approaches to the management of patients with AT deficiency in the acute and chronic settings. An extensive literature search of Scopus (January 2008-April 2016) was performed for the terms congenital antithrombin deficiency, inherited antithrombin deficiency, or hereditary antithrombin deficiency Additional references were identified by reviewing literature citations. All relevant English-language case reports, reviews, clinical studies, meeting abstracts, and book chapters assessing hereditary AT deficiency were included. AT deficiency significantly increases the risk of venous thromboembolism (VTE). The risk of VTE is particularly high during pregnancy, the postpartum period, and following major surgery. Effective clinical management includes determination of the appropriate type and duration of antithrombotic therapy (ie, AT replacement for acute situations) while minimizing the risk of bleeding. For persons newly diagnosed with AT deficiency, age, lifestyle, concurrent medical conditions, family history, and personal treatment preferences can be used to individualize patient management. Patients should be informed of the risks associated with hormonal therapy, pregnancy, surgical procedures, and immobility, which further increase the risk of VTE in patients with AT deficiency. AT deficiency poses the highest risk for VTE among the hereditary thrombophilias, often requiring long-term anticoagulation. Undertaking an evaluation for hereditary thrombophilia is controversial; however, a diagnosis of VTE in association with AT deficiency can have management implications. An important treatment option for patients with this disorder in high-risk situations is AT concentrate.

The functional study of antithrombin L99 mutation

To study the molecular mechanisms of inherited antithrombin (AT) deficiency caused by AT L99 mutation. Wild type (WT), L99V, L99A, L99I and L99S AT were purified from drosophila expression system. The binding capacity of AT and the low molecular weight heparin sodium was analyzed by the heparin binding assay. Surface plasmon resonance (SPR) was used to detect the binding ability of AT to thrombin (FIIa) or AT to coagulation factor Xa (FXa). The activity of AT(AT∶A)was detected by chromogenic assay. The purified WT and mutant AT were at the same size. No additional band was observed by coomassie blue staining and western blot assay. Compared to the WT AT, the binding abilities of the low molecular weight heparin sodium to the AT L99V, L99A, L99I and L99S were (44.8±3.6)%, (118.9±14.0)%, (15.2±8.8)%, and(23.0±8.2)%, respectively. The binding abilities of FIIa to AT L99V, L99A, L99I and L99S were 13%, 57%, 3%, and 29%, while the binding of FXa to AT L99V, L99A, L99I and L99S were 7%, 51%, 1%, and 25%. The AT∶A of WT, L99V, L99A, L99I and L99S AT were 146.5%, 21.4%, 120.9%, 10.8%, and 39.0%, respectively. The binding abilities of AT to heparin, FIIa and FXa were damaged by the L99 mutation, which resulted in decreased AT∶A and inherited AT deficiency.