Distinct frequencies and mutation spectrums of genetic thrombophilia in Korea in comparison with other Asian countries both in patients with thromboembolism and in the general population

The risk profiles of pregnancy-related cerebral venous thrombosis: a retrospective study in a comprehensive hospital

OBJECTIVES

To investigate the risk factors and underlying causes of pregnancy-related cerebral venous thrombosis (PCVT).

METHODS

A retrospective cohort of 16 patients diagnosed with CVT during pregnancy and postpartum (within six weeks after delivery) in a comprehensive hospital in China between 2009 and 2022 were carefully reviewed, focusing on demographic, clinical, and etiological characteristics, especially underlying causes. We matched 16 PCVT patients with 64 pregnant and puerperal women without PCVT to explore risk factors and clinical susceptibility to PCVT.

RESULTS

PCVT occurred commonly during the first trimester (43.75%) and the puerperium (37.5%). The frequency of anemia, thrombocytosis and thrombocytopenia during pregnancy, dehydration, and pre-pregnancy anemia was significantly higher in women with PCVT than in those without PCVT (P < 0.05). Among the 16 patients, five were diagnosed with antiphospholipid syndrome and one was diagnosed with systemic lupus erythematosus. Three patients had distinct protein S deficiency and one had protein C deficiency. Whole Exome Sequencing (WES) was performed for five patients and revealed likely pathogenic mutations associated with CVT, including heterozygous PROC c.1218G > A (p. Met406Ile), heterozygous PROS1 c.301C > T (p. Arg101Cys), composite heterozygous mutation in the F8 gene (c.144-1259C > T; c.6724G > A (p. Val2242Met)) and homozygous MTHFR c.677C > T (p. Ala222Val).

CONCLUSIONS

The occurrence of anemia, thrombocytopenia and thrombocytosis during pregnancy, dehydration and pre-pregnancy anemia suggested a greater susceptibility to PCVT. For confirmed PCVT patients, autoimmune diseases, hereditary thrombophilia, and hematological disorders were common causes. Screening for potential etiologies should be paid more attention, as it has implications for treatment and long-term management.

Validation for the function of protein C in mouse models

Objectives

Protein C (PC) is an anticoagulant that is encoded by the PROC gene. Validation for the function of PC was carried out in mouse models.

Methods

In this study, autosomal recessive PC deficiency (PCD) was selected as the target, and the specific mutation site was chromosome 2 2q13-q14, PROC c.1198G>A (p.Gly400Ser) which targets G399S (GGT to AGC) in mouse models. To investigate the role of hereditary PC in mice models, we used CRISPR/Cas9 gene editing technology to create a mouse model with a genetic PCD mutation.

Results

The two F0 generation positive mice produced using the CRISPR/Cas9 gene editing technique were chimeras, and the mice in F1 and F2 generations were heterozygous. There was no phenotype of spontaneous bleeding or thrombosis in the heterozygous mice, but some of them were blind. Blood routine results showed no significant difference between the heterozygous mice and wild-type mice (P > 0.05). Prothrombin time (PT), activated partial thromboplastin time (APTT), and thrombin time (TT) were prolonged in the heterozygous mice, while the level of fibrinogen content (FIB) decreased, suggesting secondary consumptive coagulation disease. The protein C activity of heterozygous mice was significantly lower than that of wild-type mice (P < 0.001), but there was no significant difference in protein C antigen levels (P > 0.05). H&E staining showed steatosis and hydrodegeneration in the liver of heterozygous mice. Necrosis and exfoliated epithelial cells could be observed in renal tubule lumen, forming cell or granular tubules. Hemosiderin deposition was found in the spleen along with splenic hemorrhage. Immunohistochemistry demonstrated significant fibrin deposition in the liver, spleen, and kidney of heterozygous mice.

Conclusion

In this study, heterozygotes of the mouse model with a PC mutation were obtained. The function of PC was then validated in a mouse model through genotype, phenotype, and PC function analysis.

The clinical and genetic landscape of early-onset thrombophilia in Japan

OBJECTIVES

To determine the optimal management for early-onset thrombophilia (EOT), the genetic and clinical features of protein C (PC)-, protein S (PS)-, or antithrombin (AT)-deficient patients of ≤20 years of age were studied in Japan.

METHODS/RESULTS

Clinical and genetic information of all genetically diagnosed cases was collected through the prospective, retrospective study, and literature review. One-hundred-one patients had PC (n = 55), PS (n = 29), or AT deficiency (n = 18). One overlapping case had PC- and PS-monoallelic variant. Fifty-five PC-deficient patients (54%) had 26 monoallelic or 29 biallelic variant(s), and 29 (29%) PS-deficient patients had 20 monoallelic or nine biallelic variant(s). None of the patients had AT-biallelic variants. The frequent low-risk allele p.K193del (PC-Tottori) was found in five patients with monoallelic (19%) but not 29 with biallelic variant(s). The most common low-risk allele p.K196E (PS-Tokushima) was found in five with monoallelic (25%) and six with biallelic variant(s) (67%). One exceptional de novo PC variant was found in 32 families with EOT. Only five parents had a history of thromboembolism. Thrombosis concurrently developed in three mother-newborn pairs (two PC deficiency and one AT deficiency). The prospective cohort revealed the outcomes of 35 patients: three deaths with PC deficiency and 20 complication-free survivors. Neurological complications were more frequently found in patients with PC-biallelic variants than those with PC-, PS-, or AT-monoallelic variants (73% vs. 24%, p = .019).

CONCLUSIONS

We demonstrate the need for elective screening for EOT targeting PC deficiency in Japan. Early prenatal diagnosis of PC deficiency in mother-infant pairs may prevent perinatal thrombosis in them.

Congenital thrombophilia in East-Asian venous thromboembolism population: a systematic review and meta-analysis

Background

Various inherited traits contribute to the overall risk of venous thromboembolism (VTE). In addition, the epidemiology of thrombophilia in the East-Asian VTE population remains unclear; thus, we aimed to assess the proportion of hereditary thrombophilia via a meta-analysis.

Methods

Publications from PubMed, EMBASE, web of science, and Cochrane before December 30, 2022, were searched. Studies from Japan, Korea, China, Hong Kong, Taiwan, Singapore, Thailand, Vietnam, Myanmar, and Cambodia were included. Congenital thrombophilia was described as diseases including protein C (PC) deficiency, protein S (PS) deficiency, antithrombin (AT) deficiency, factor (F)V Leiden (FVL), and prothrombin G20210A mutations. Studies were selected by 2 reviewers for methodological quality analysis. A random-effects model was used for the meta-analysis, assuming that estimated effects in the different studies are not identical.

Results

Forty-four studies involving 6453 patients from 7 counties/regions were included in the meta-analysis. The prevalence of PC, PS, and AT deficiencies were 7.1%, 8.3%, and 3.8%, respectively. Among 2924 patients from 22 studies, 5 patients were carriers of FVL mutation. Among 2196 patients from 10 studies, 2 patients were carriers of prothrombin G20210A mutation in a Thailand study.

Conclusion

The prevalence of PC, PS, and AT deficiencies was relatively high, while a much lower prevalence of FVL and prothrombin G20210A mutations were identified in East-Asian patients with VTE. Our data stress the relative higher prevalence of PC, PS, and AT deficiencies for thrombophilia in the East-Asian VTE population.

Surgical treatment of traction retinal detachment associated with compound heterozygous congenital protein C deficiency

Purpose

Congenital protein C deficiency leads to a prothrombotic state that may result in potentially sight- and life-threatening thromboembolic attacks. In this report, we report two cases of infants with compound heterozygous protein C deficiency who underwent lensectomies and vitrectomies for the treatment of traction retinal detachments (TRDs).

Observations

One two-month-old and one three-month-old female neonates with leukocoria and purpura fulminans received a diagnosis of protein C deficiency and were referred to ophthalmology. In both cases, the right eye had a total retinal detachment that was considered inoperable, while the left eye had a partial TRD for which surgery was performed. Of the two operated eyes, one resulted in a total retinal detachment, while the other eye has remained stable with no retinal detachment progression three months after surgery.

Conclusions

Compound heterozygous congenital protein C deficiency may lead to the rapid development of severe TRDs with poor visual and anatomical prognoses. Early diagnosis and surgery for the treatment of partial TRDs with low disease activity may help prevent progression towards total retinal detachments in these infants.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Modern Aspects of Anticoagulation System Disorders Diagnosis in Children with Different Polymorphisms in Coagulation Genes. Initial Results

Background. Hemostatic system pathology is topical and poorly studied issue in pediatrics. One of the main causes of coagulation pathway disorders associated with thrombotic events is abnormality in various parts of the hemostatic system. Vascular accidents are commonly caused by anticoagulation system factors deficiency. Conventionally, thrombosis is a common event in adult patients, and there is no adequate attention to disorders of primary physiological anticoagulants system in children. More often acquired anticoagulant proteins deficiency develops in presence of various pathological conditions, especially after the past infectious diseases. All these diseases (thrombophilia, trombotic events, cardiovascular pathology, nervous system diseases, genetic diseases) can occur separately and in association with each other, plus clinical picture of coagulation events may be similar. Objective. The aim of the study is to evaluate changes in the physiological anticoagulants system in children with different pathologies who have polymorphic variants in coagulation genes and who had new coronavirus infection. Methods. The study included 33 children who had severe coronavirus infection in family clusters and had severe chronic pathology potentially associated with disorders of the coagulation system (nervous system damage, hypertrophic cardiomyopathy, hereditary monogenic syndromes, hemato-mesenchymal dysplasia syndrome). All children underwent complete examination including clinical examination, laboratory, and instrumental diagnostics. Results. Preliminary study results indicate significant incidence of polymorphic variants in coagulation genes (one third of children with various diseases from the study). Some children had decreased activity of anticoagulation system glycoproteins (from 6% to 36%) that confirmed the topicality of the examination of anticoagulation system factors deficiency and the need for further dynamic follow-up, as well as revealing of trombophilia predictors in children in selected target groups. Study on revealing anticoagulation system disorders and mutations in coagulation genes will predict the risk of thrombotic disorders. Conclusion. The obtained results have confirmed the significant role of the ongoing study for comprehensive assessment of hemostatic system disorders in children. That will allow us to optimize the approach to diagnosis and personalize the management strategy for patients with different chronic pathologies and disorders of the natural anticoagulants system. The study is currently ongoing.

Protein S Deficiency and the Risk of Venous Thromboembolism in the Han Chinese Population

Plasma levels of the anticoagulant cofactor protein S and PROS1 mutation are reported to impart increased risk of thromboembolism in European and south east Asian populations, but the relationship is not yet documented in Han Chinese in population-based study. Therefore, we undertook a case-control study of this relationship among patients with venous thromboembolism, and probed the genetic factors contributing to low protein S deficiency. Among the 603 consecutively recruited venous thromboembolism patients, 51 (8.5%) proved to be deficient in free protein S antigen (lower than 38.6 U/dl), among whom 30 cases were identified to have a causative mutation by direct sequencing. In contrast, six cases (1.0%) of the 584 healthy controls had low free antigen levels, among whom direct sequencing confirmed disease-causing gene mutations in four controls (0.7%). After adjusting for age and gender, the odds ratio of developing venous thromboembolism in individuals with protein S deficiency based on free protein S tests was 8.1 (95% CI = 3.6–19.9, P < 0.001). Gene sequencing yielded 24 different heterozygous mutations in the 34 participants, of which 13 were newly described. 17 (50%) of the 34 mutations in our study cohort occurred in exons 12 and 13, indicating the LGR2 domain to be a hotspot mutation region for the protein. These findings are conducive to the clinical application of protein S assays for the molecular diagnosis of thrombophilia.

Utility of the SERPINC1 Gene Test in Ischemic Stroke Patients With Antithrombin Deficiency

Objective

Antithrombin (AT) plays a critical role in the coagulation system, and its deficiency induces hypercoagulability. AT deficiency is caused not only by inherited variants in the SERPINC1 gene but also by acquired conditions. Therefore, AT deficiency alone could not ensure the presence of the SERPINC1 mutation. We evaluated the utility of the SERPINC1 gene test in ischemic stroke, an important clinical type of arterial thrombosis.

Methods

This retrospective, observational study investigated symptomatic patients who underwent the SERPINC1 gene test because of decreased AT activity (&lt;80%) during 2009-2021 at a tertiary hospital. For the detection of sequence variants in the SERPINC1 gene, direct Sanger sequencing and multiplex ligation-dependent probe amplification were performed. The phenotypes of patients with SERPINC1 gene mutations were examined, and the conditions associated with the pathogenic variants were analyzed.

Results

In our cohort (n = 19), 13 of 19 patients (68.4%) had the pathogenic variant of the SERPINC1 gene. Ischemic stroke (n = 7) was significantly associated with the pathogenic variants (p = 0.044), and the pathogenicity detection rate was 100%. For any kind of arterial thrombosis (n = 8), the detection rate of the pathogenic variant was 87.5%, but was not statistically significant (p = 0.177). The detection rates of the pathogenic variant in ischemic stroke or arterial thrombosis groups were both higher than those in the venous thrombosis-only group (54.5%).

Conclusion

The SERPINC1 gene test was useful in determining the cause of AT deficiency-related arterial thrombosis, especially ischemic stroke. We propose the diagnostic flow of SERPINC1-related ischemic stroke.

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.

Detection of Unknown and Rare Pathogenic Variants in Antithrombin, Protein C and Protein S Deficiency Using High-Throughput Targeted Sequencing

The deficiency of natural anticoagulants—antithrombin (AT), protein C (PC), and protein S (PS)—is a highly predisposing factor for thrombosis, which is still underdiagnosed at the genetic level. We aimed to establish and evaluate an optimal diagnostic approach based on a high-throughput sequencing platform suitable for testing a small number of genes. A fast, flexible, and efficient method involving automated amplicon library preparation and target sequencing on the Ion Torrent platform was optimized. The cohort consisted of a group of 31 unrelated patients selected for sequencing due to repeatedly low levels of one of the anticoagulant proteins (11 AT-deficient, 13 PC-deficient, and 7 PS-deficient patients). The overall mutation detection rate was 67.7%, highest in PC deficiency (76.9%), and six variants were newly detected—SERPINC1 c.398A > T (p.Gln133Leu), PROC c.450C > A (p.Tyr150Ter), c.715G > C (p.Gly239Arg) and c.866C > G (p.Pro289Arg), and PROS1 c.1468delA (p.Ile490fs) and c.1931T > A (p.Ile644Asn). Our data are consistent with those of previous studies, which mostly used time-consuming Sanger sequencing for genotyping, and the indication criteria for molecular genetic testing were adapted to this process in the past. Our promising results allow for a wider application of the described methodology in clinical practice, which will enable a suitable expansion of the group of indicated patients to include individuals with severe clinical findings of thrombosis at a young age. Moreover, this approach is flexible and applicable to other oligogenic panels.

Severe dysplasminogenemia due to homozygous PLG Ala620Thr variant in a Korean woman without a history of venous thromboembolism: A case report and literature review

RATIONALE

Plasminogen plays an important role in fibrinolysis and is encoded by the PLG gene. The missense variant PLG Ala620Thr is the major cause of dysplasminogenemia in East Asian countries, including Korea. Although dysplasminogenemia was first reported in a Japanese patient with recurrent venous thromboembolism (VTE), subsequent studies have not demonstrated any clear association between the PLG Ala620Thr variant and the risk of VTE. To the best of our knowledge, this is the first report of a homozygous PLG Ala620Thr variant case from Korea.

PATIENT CONCERNS

Here, we report a Korean family with PLG Ala620Thr mutation. The proband was a 34-year-old man who presented with multiple thrombotic arterial embolism and cardiac myxoma.

INTERVENTIONS

Laboratory workup, including coagulation profile and PLG gene sequencing, was carried out for the affected family.

DIAGNOSIS AND OUTCOME

The proband carried a heterozygous PLG Ala620Thr variant with decreased plasminogen activity of 65%. His 53-year-old mother, who had no reported history of VTE, was homozygous for the PLG Ala620Thr variant with decreased plasminogen activity of just 25%. Decreased plasminogen activity indicates dysplasminogenemia.

LESSONS

We believe that this clinically silent homozygous case supports the previous findings that isolated PLG Ala620Thr variant does not confer a significant risk of VTE.

Heritable Thrombophilia in Venous Thromboembolism in Northern Pakistan: A Cross-Sectional Study

BACKGROUND

Venous thromboembolism (VTE) is referred to as formation of clots in a deep vein or lodging of thrombus towards the lungs which could be fatal yet preventable. The risk of developing VTE can be increased by various factors. Where there are innumerable acquired causes, the possibility of inherited thrombophilia cannot be ignored. In view of this, we have evaluated all patients with venous thromboembolism for inherited thrombophilia.

OBJECTIVE

To evaluate the frequencies of antithrombin (AT) deficiency, protein C and S deficiencies, Factor V Leiden, and prothrombin gene mutations in patients harboring venous thromboembolism.

MATERIALS AND METHODS

A study comprising of 880 patients who were presented with manifestations of venous thromboembolism was conducted from July 2016 to June 2017. A blood sample collected from patients was screened for thrombophilia defects encompassing AT, protein C and S deficiencies, Factor V Leiden, and prothrombin gene mutations. All acquired causes of thrombosis were excluded.

RESULTS

Of 880 patients who underwent screening for thrombophilia, 182 patients demonstrated VTE history. Their age ranged from 1 to 58 years. Males constituted a predominant group. About 45 (24.7%) patients had evidence of heritable thrombophilia. Of these, 20 (10.9%) had AT deficiency, 9 (4.9%) had Factor V Leiden mutation, 6 (3.2%) had protein C deficiency, whereas protein S deficiency and prothrombin gene mutation both were found in 5 (2.7%) patients.

CONCLUSION

Our study illustrated the highest frequency of antithrombin deficiency among other investigated thrombophilia defects.

Severe protein C deficiency in a newborn caused by a homozygous pathogenic variant in the PROC gene: a case report

Background

Severe protein C deficiency is a rare and inherited cause of thrombophilia in neonates. Protein C acts as an anticoagulant, and its deficiency results in vascular thrombosis. Herein, we report a case of protein C deficiency with a homozygous pathogenic variant in a term neonate, with good outcomes after proper treatment.

Case presentation

A four-day-old male newborn was transferred to the Seoul National University Hospital on account of dark red to black skin lesions. He was born full-term with an average birth weight without perinatal problems. There were no abnormal findings in the prenatal tests, including intrauterine sonography. The first skin lesion was observed on his right toes and rapidly progressed to proximal areas, such as the lower legs, left arm, and buttock. Under the impression of thromboembolism or vasculitis, we performed a coagulopathy workup, which revealed a high D-dimer level of 23.05 μg/ml. A skin biopsy showed fibrin clots in most capillaries, and his protein C activity level was below 10%, from which we diagnosed protein C deficiency. On postnatal day 6, he experienced an apnea event with desaturation and an abnormal right pupillary light reflex. Brain computed tomography showed multifocal patchy intracranial hemorrhage and intraventricular hemorrhage with an old ischemic lesion. Ophthalmic examination revealed bilateral retinal traction detachments with retinal folds. Protein C concentrate replacement therapy was added to previous treatments including steroids, prostaglandin E1, and anticoagulation. After replacement therapy, there were no new skin lesions, and the previous lesions recovered with scarring. Although there were no new brain hemorrhagic infarctions, there was ongoing ischemic tissue loss, which required further rehabilitation. Ophthalmic surgical interventions were performed to treat the bilateral retinal traction detachments with retinal folds. Molecular analysis revealed a homozygous pathogenic variant in the PROC gene.

Conclusion

Severe protein C deficiency can manifest as a fatal coagulopathy in any organ. Early diagnosis and proper treatment, including protein C concentrate replacement, may improve outcomes without serious sequelae.

A thrombophilia family with protein S deficiency due to protein translation disorders caused by a Leu607Ser heterozygous mutation in PROS1

BACKGROUND

Protein S deficiency (PSD) is an autosomal dominant hereditary disease. In 1984, familial PSD was reported to be prone to recurrent thrombosis. Follow-up studies have shown that heterozygous protein S (PROS1) mutations increase the risk of thrombosis. More than 300 PROS1 mutations have been identified; among them, only a small number of mutations have been reported its possible mechanism to reduce plasma protein S (PS) levels. However, whether PROS1 mutations affect protein structure and why it can induce PSD remains unknown.

METHODS

The clinical phenotypes of the members of a family with thrombosis were collected. Their PS activity was measured using the coagulation method, whereas their protein C and antithrombin III activities were measured using methods such as the chromogenic substrate method. The proband and her parents were screened for the responsible mutation using second-generation whole exon sequencing, and the members of the family were verified for suspected mutations using Sanger sequencing. Mutant and wild type plasmids were constructed and transfected into HEK293T cells to detect the mRNA and protein expression of PROS1.

RESULTS

In this family, the proband with venous thrombosis of both lower extremities, the proband's mother with pulmonary embolism and venous thrombosis of both lower extremities, and the proband's younger brother had significantly lower PS activity and carried a PROS1 c. 1820 T > C:p.Leu607Ser heterozygous mutation (NM_000313.3). However, no such mutations were found in family members with normal PS activity. The PS expression in the cell lysate and supernatant of the Leu607Ser mutant cells decreased, while mRNA expression increased. Immunofluorescence localization showed that there was no significant difference in protein localization before and after mutation.

CONCLUSIONS

The analysis of family phenotype, gene association, and cell function tests suggest that the PROS1 Leu607Ser heterozygous mutation may be a pathogenic mutation. Serine substitution causes structural instability of the entire protein. These data indicate that impaired PS translation and synthesis or possible secretion impairment is the main pathogenesis of this family with hereditary PSD and thrombophilia.

Type II antithrombin deficiency caused by a novel missense mutation (p.Leu417Gln) in a Chinese family

THE AIM OF THE REPORT WAS T

o explore the phenotype and genotype of a hereditary antithrombin deficient Chinese family. Functional and molecular analysis of the proband and his family members was performed. Online bioinformatics software was used to predict the pathogenicity of the novel mutation. ClustalX-2.1-win and PyMol software were applied to conservative analysis and generate molecular graphic images, respectively. Functional analysis had shown that the antithrombin (AT):A of the proband was reduced to 32% whereas AT:Ag was normal. Molecular analysis revealed a heterozygous missense mutation p. Leu417Gln in exon 7 of SERPINC1 gene. Bioinformatics and model analysis indicated that this mutation could affect the integrity of local intermolecular structures, resulting in a mild type of antithrombin deficiency but when combined with other genetic or acquired thrombophilic factors, patients may develop venous thrombosis. The p.Leu417Gln mutation was responsible for the decrease of AT:A in this family and caused type II antithrombin deficiency.

Distinct genetic profile with recurrent population-specific missense variants in Korean adult atypical hemolytic uremic syndrome

INTRODUCTION

Atypical hemolytic uremic syndrome (aHUS) is a rare thrombotic microangiopathy (TMA), characterized by micro-angiopathic hemolytic anemia, thrombocytopenia, and renal failure. In more than half of cases, genetic defects leading to overactivation of the alternative complement system have been identified. In this study, we investigated genetic defects in Korean adult patients with aHUS.

MATERIALS AND METHODS

Sixty-six Korean adult patients with aHUS were ascertained from the Korean TMA Registry. Genetic variants of 15 aHUS-related genes (eight core genes [CFH, CFB, CFI, CD46, C3, THBD, PLG, and DGKE] and seven candidate genes [CFP, C4BPA, and CHFR1-5]) were analyzed from exome sequencing data. Multiplex ligation-dependent probe amplification of CFH and related genes was performed to detect hybrid genes or large deletions.

RESULTS

Thirty patients (45%) had at least one aHUS-related variant (s) in eight core genes (total 40 variant alleles). The most frequently affected gene was CFH (13/40, 32%), followed by THBD (8/40, 20%) and CD46 (7/40, 18%). The two most common variants were Asp486Tyr of THBD (N = 7) and Tyr1058His-Val1060Leu of CFH (N = 5, linked on the same allele), accounting for 30% (12/40). In seven candidate genes, 19 variants were detected. When combined, 40 patients (61%) had at least one variant in 15 core or candidate genes. No patients had anti-CFH Ab or hybrid gene/CFHR1 homozygous deletions.

CONCLUSIONS

The genetic profile of Korean adult aHUS was unique with recurrent missense variants, demonstrating ethnicity- and age-dependent differences in the genetic background of aHUS.

Recurrent PROC and novel PROS1 mutations in Vietnamese patients diagnosed with idiopathic deep venous thrombosis

INTRODUCTION

Genetic mutations of PROC and PROS1 are well-known risk factors for deep venous thrombosis (DVT) in the Asian population. However, the genetic profile of Vietnamese patients with DVT remains elusive. This study aimed to investigate the spectrum of genetic mutations of these two genes in Vietnamese patients diagnosed with idiopathic DVT.

MATERIALS AND METHODS

A total of 50 Vietnamese patients diagnosed with idiopathic DVT were recruited in this study. The entire coding regions of the protein C and protein S genes were amplified and directly sequenced to determine genetic alterations.

RESULTS

Four and six genetic mutations were detected in protein C and protein S genes, respectively, in 24 Vietnamese DVT patients. PROC c.565C > T (p.R189W) was the most common mutation found in 13 out of 50 patients, while the mutations of PROS1 comprised three missense and three nonsense variants which diffuse along the gene.

CONCLUSIONS

This study shows that mutations of protein C and protein S genes are prevalent in Vietnamese patients diagnosed with idiopathic DVT, and PROC c.565C > T (p.R189W) was the most common genetic alteration.

PROC Promoter Single Nucleotide Polymorphisms Associated With Low Protein C Activity But Not Increased Risk of Thromboembolism in Pediatric Population

Protein C (PC) deficiency, caused by mutations of the PROC gene, is a common inherited risk factor of thromboembolism (TE) among Thai people. This study aimed to investigate the association of 3 single nucleotide polymorphisms (SNPs; −1654 C/T, −1641 A/G, −1461A/T) at the PROC promoter region with PC activity and the risk of developing TE. A total of 216 patient s with TE, diagnosed at aged 0 to 20 years, and 102 healthy adults were enrolled. The SNPs were identified by Sanger sequencing. Protein C activity was measured using an automated functional clotting assay. Linear and logistic regression analyses were used to determine the association of SNPs with PC activity and the risk of TE. Patients and controls with homozygous TAA (119.6% ± 26.1%) and CGT haplotypes (102.7% ± 22.6%) had significantly lower PC activity than those with a homozygous CAA haplotype (140.4% ± 44.9%); P = .027 and .016, respectively. However, none of these haplotypes increased the risk of TE. This study suggested that the 3 PROC promoter SNPs were shown to be associated with lower PC activity but did not increase the risk of TE.

Association of SERPINC1 Gene Polymorphism (rs2227589) With Pulmonary Embolism Risk in a Chinese Population

Background and Aims: Genetic variants in the gene SERPINC1 have been shown to be associated with antithrombin deficiency, which subsequently contributes to the susceptibility to venous thrombosis. However, several other studies have shown conflicting results regarding the association of SERPINC1 gene polymorphisms (rs2227589) with the risk of thrombosis. Hence, in the present study, we conducted a case-control study to further evaluate the association between the variant rs2227589 with antithrombin deficiency in pulmonary embolism (PTE). A pooled systematic analysis was also conducted to evaluate the risk of rs2227589 in venous thromboembolism (VTE) among multiple populations. Methods: This case-control study involved 101 patients and 199 healthy controls. The allele frequency of SERPINC1 variant rs2227589 was analyzed by Sequenom assay. Antithrombin anticoagulant activity was detected using an automatic coagulation analyzer. In addition, a pooled systematic analysis on 10 cohorts consisting of 5,518 patients with VTE and 8,935 controls was performed. Results: In total, 27 (26.7%) PTE subjects were diagnosed as having antithrombin deficiency. Our results showed that antithrombin plasma activity was slightly lower in T allele carriers than that in C allele carriers. However, there was no significant correlation between rs2227589 genotype and antithrombin anticoagulant activity. The recessive model showed that rs2227589 was significantly associated (p = 0.026) with an increased risk {odds ratio [OR]: 2.31, 95% confidence interval [CI] (1.09-4.89)} of Chinese PTE. The pooled systematic analysis of all case-control study and meta-analysis showed that rs2227589 polymorphism was associated with an increased risk of VTE in the additive model [OR: 1.09, 95% CI (1.01-1.18), P = 0.029] and dominant model [OR: 1.10, 95% CI (1.01-1.20), P = 0.034]. Conclusions: Our study demonstrated that variant rs2227589 is associated with an increased risk of PTE in a Chinese population but no correlation with antithrombin anticoagulant activity. However, pooled systematic analysis of multiple populations showed a significant association between rs2227589 and the risk of VTE in the additive and dominant genetic model.

Genetic analysis should be included in clinical practice when screening for antithrombin deficiency

Antithrombin (AT) deficiency increases the risk of thrombosis. Current evidence shows that some SERPINC1 mutations responsible for antithrombin deficiency often present a slightly decreased or normal activity and therefore could not be detected by functional tests. This study was designed to compare activity assays and direct genetic analyses in identifying hereditary antithrombin deficiency. In total, 400 consecutive patients with venous thrombosis were enrolled. Functional assays showed that 16 of the 400 individuals had decreased antithrombin activity, and 14 of them were confirmed by genetic analysis. Of the remaining 384 patients, 95 individuals without a known risk factor and 95 individuals with predisposing factors were also selected for gene sequencing. Eight additional causative mutations were identified in nine individuals and they should also be considered as antithrombin deficiency. In addition, a recurrent mutation, p.Arg356_Phe361del, was characterised. The mutant appeared to have a partially impaired secretion and a reduction in functional activity by 50 %. This study indicated that including genetic analysis in screening tests for identifying antithrombin deficiency was essential. Specifically, a genetic analysis of SERPINC1 is strongly recommended when individuals experience unprovoked thrombotic diseases, even if the AT activities are normal.

The prevalence and clinical manifestation of hereditary thrombophilia in Korean patients with unprovoked venous thromboembolisms

Background

Hereditary thrombophilia (HT) is a genetic predisposition to thrombosis. Asian mutation spectrum of HT is different from Western ones. We investigated the incidence and clinical characteristics of HT in Korean patients with unprovoked venous thromboembolism (VTE).

Methods

Among 369 consecutive patients with thromboembolic event who underwent thrombophilia tests, we enrolled 222 patients diagnosed with unprovoked VTE. The presence of HT was confirmed by DNA sequencing of the genes that cause deficits in natural anticoagulants (NAs). Median follow-up duration was 40±38 months.

Results

Among the 222 patients with unprovoked VTE, 66 (29.7%) demonstrated decreased NA level, and 33 (14.9%) were finally confirmed to have HT in a genetic molecular test. Antithrombin III deficiency (6.3%) was most frequently detected, followed by protein C deficiency (5.4%), protein S deficiency (1.8%), and dysplasminogenemia (1.4%). The HT group was significantly younger (37 [32–50] vs. 52 [43–65] years; P < 0.001) and had a higher proportion of male (69.7% vs. 47%; P = 0.013), more previous VTE events (57.6% vs. 31.7%; P = 0.004), and a greater family history of VTE (43.8% vs. 1.9%; P < 0.001) than the non-HT group. Age <45 years and a family history of VTE were independent predictors for unprovoked VTE with HT (odds ratio, 9.435 [2.45–36.35]; P = 0.001 and 92.667 [14.95–574.29]; P < 0.001).

Conclusions

About 15% of patients with unprovoked VTE had HT. A positive family history of VTE and age <45 years were independent predictors for unprovoked VTE caused by HT.

The clinical presentation and genotype of protein C deficiency with double mutations of the protein C gene

BACKGROUND

Severe protein C (PC) deficiency is a rare heritable thrombophilia leading to thromboembolic events during the neonatal period. It remains unclear how individuals with complete PC gene (PROC) defects develop or escape neonatal stroke or purpura fulminans (PF).

PROCEDURE

We studied the onset of disease and the genotype of 22 PC-deficient patients with double mutations in PROC based on our cohort (n = 12) and the previous reports (n = 10) in Japan.

RESULTS

Twenty-two patients in 20 unrelated families had 4 homozygous and 18 compound heterozygous mutations. Sixteen newborns presented with PF (n = 11, 69%), intracranial thromboembolism and hemorrhage (n = 13, 81%), or both (n = 8, 50%), with most showing a plasma PC activity of <10%. Six others first developed overt thromboembolism when they were over 15 years of age, showing a median PC activity of 31% (range: 19-52%). Fifteen of the 22 patients (68%) had the five major mutations (G423VfsX82, V339M, R211W, M406I, and F181V) or two others (E68K and K193del) that have been reported in Japan. Three of the six late-onset cases, but none of the 16 neonatal cases, had the K193del mutation, which has been reported to be the most common variant of Chinese thrombophilia. A novel mutation of A309V was determined in a family of two patients with late onset.

CONCLUSIONS

The genotype of double-PROC mutants might show less diversity than heterozygous mutants in terms of the timing of the onset of thrombophilia (newborn onset or late onset).

Whole-exome sequencing in evaluation of patients with venous thromboembolism

Genetics play a significant role in venous thromboembolism (VTE), yet current clinical laboratory-based testing identifies a known heritable thrombophilia (factor V Leiden, prothrombin gene mutation G20210A, or a deficiency of protein C, protein S, or antithrombin) in only a minority of VTE patients. We hypothesized that a substantial number of VTE patients could have lesser-known thrombophilia mutations. To test this hypothesis, we performed whole-exome sequencing (WES) in 64 patients with VTE, focusing our analysis on a novel 55-gene extended thrombophilia panel that we compiled. Our extended thrombophilia panel identified a probable disease-causing genetic variant or variant of unknown significance in 39 of 64 study patients (60.9%), compared with 6 of 237 control patients without VTE (2.5%) (P < .0001). Clinical laboratory-based thrombophilia testing identified a heritable thrombophilia in only 14 of 54 study patients (25.9%). The majority of WES variants were either associated with thrombosis based on prior reports in the literature or predicted to affect protein structure based on protein modeling performed as part of this study. Variants were found in major thrombophilia genes, various SERPIN genes, and highly conserved areas of other genes with established or potential roles in coagulation or fibrinolysis. Ten patients (15.6%) had >1 variant. Sanger sequencing performed in family members of 4 study patients with and without VTE showed generally concordant results with thrombotic history. WES and extended thrombophilia testing are promising tools for improving our understanding of VTE pathogenesis and identifying inherited thrombophilias.

Whole Exome Sequencing Reveals Severe Thrombophilia in Acute Unprovoked Idiopathic Fatal Pulmonary Embolism

BACKGROUND

Acute unprovoked idiopathic fatal pulmonary embolism (IFPE) causes sudden death without an identifiable thrombogenic risk. We aimed to investigate the underlying genomic risks of IFPE through whole exome sequencing (WES).

METHODS

We reviewed 14years of consecutive out-of-hospital fatal pulmonary embolism records (n=1478) from the ethnically diverse population of New York City. We selected 68 qualifying IFPE cases for WES. We compared the WES data of IFPE cases to those of 9332 controls to determine if there is an excess of rare damaging variants in the genome using ethnicity-matched controls in collapsing analyses.

FINDINGS

We found nine of the 68 decedents (13·2%) who died of IFPE had at least one pathogenic or likely pathogenic variant in one of the three anti-coagulant genes: SERPINC1 (Antithrombin III), PROC, and PROS1. The odds ratio of developing IFPE as a variant carrier for SERPINC1 is 144·2 (95% CI, 26·3-779·4; P=1·7×10-7), for PROC is 85·6 (95% CI, 13·0-448·9; P=2.0×10-5), and for PROS1 is 56·4 (95% CI, 5·3-351·1; P=0·001). The average age-at-death of anti-coagulant gene variant carriers is significantly younger than that of non-carriers (28·56years versus 38·02years; P=0·01).

INTERPRETATION

This study showed the important role of severe thrombophilia due to natural anti-coagulant deficiency in IFPE. Evaluating severe thrombophilia in out-of-hospital fatal PE beyond IFPE is warranted.

Causative genetic mutations for antithrombin deficiency and their clinical background among Japanese patients

We summarize causative genetic mutations for antithrombin (AT) deficiency and their clinical background in Japanese patients. A total of 19 mutations, including seven novel mutations, were identified. We also summarize clinical symptoms of thrombosis, age at onset, family history, and contributing factors for thrombosis, and review the use of prophylactic anticoagulation in pregnant women with heterozygous type II heparin binding site defects (HBS) AT deficiency. The prevalence of thrombosis in probands with type I AT deficiency (88%) was double that observed in those with type II AT deficiency (50%). The prevalence of thrombotic episodes among family members was also higher for type I AT deficiency subjects (82%) than for those with type II AT deficiency (0%). The most common contributing factor for thrombosis among women with type I AT deficiency was pregnancy. Forty-five percent of women with type I AT deficiency developed thrombotic events before the 20th week of gestation. In contrast, women with type II (HBS) AT deficiency appear to be at a lower risk of thrombosis during pregnancy. In conclusion, thrombotic risk varies among different subtypes. Risk assessments based on genetic/clinical backgrounds may contribute to appropriate diagnosis, treatment, and prophylaxis for patients with AT deficiency.

Subtypes of SERPINC1 mutations and the thrombotic phenotype of inherited antithrombin deficient individuals in Chinese Han population

Inherited antithrombin (AT) deficiency is a rare autosomal disease that could increase the risk of venous thromboembolism (VTE) and usually caused by mutations of SERPINC1. Although a number of mutations of SERPINC1 have been reported in Chinese Han population, the impact of different subtypes of these mutations on the thrombotic phenotype is still unknown. Here, we performed a retrospective cohort study including 169 AT patients from 63 families to compare the clinical features between null mutation carriers and missense mutation carriers. We found that patients carrying null mutations have a higher risk of VTE (HR 2.29, 95% CI 1.16-4.69, P=0.02 adjusted for sex and VTE family history) and earlier median onset age of VTE (27 vs. 32years, P=0.045) as well as lower AT activities (47.6±1.0% vs. 59.1±2.3%, P<0.001) than those with missense mutations. We also observed that thrombus location sites showed no difference between null mutation carriers and missense mutation carriers, gene locations of the mutations did not relate with the incidence rate of VTE. This study demonstrated that different types of SERPINC1 mutations may play different roles in the development of VTE and should be considered in the prevention of VTE.

Thrombophilia in East Asian countries: are there any genetic differences in these countries?

In recent years, genetic analyses of congenital deficiencies of three anticoagulant proteins, antithrombin, protein C (PC) and protein S (PS), in East Asian patients with venous thromboembolism (VTE) have greatly increased. The PS-K196E mutation is often identified in the Japanese population with an allelic frequency of 0.86 %, and a total of approximately 10,000 Japanese are estimated to be homozygotes. The heterozygotes show PS anticoagulant activities ranging from 40 to 110 %, and 16 % lower mean anticoagulant activity than that in wild-type individuals. Specific assay methods to identify carriers of this mutation have recently been developed. The mutation carriers are at risk of thrombosis during pregnancy but do not appear to be at risk for adverse pregnancy outcomes. To promote future research into this mutation and its relation to thrombosis, a thrombosis-prone mouse strain with the PS K196E mutation has been developed. We found the PS-K196E mutation and the heterozygous PS-deficiency in mice caused increased VTE, but did not cause aggravation of ischemic stroke, unlike factor V Leiden mutation. Importantly, the PS-K196E mutation is only identified in Japanese. This suggests that although East Asian populations including Japanese, Chinese, and Koreans are geographically and genetically close, the PS-K196E mutation seems to be Japanese-specific, suggesting that the mutation is a recent occurrence and fixed within the Japanese population. Some recurrent genetic mutations predisposing to VTE have been reported in Chinese and Korean populations. Although the genetic background for VTE is known to differ between populations with Caucasian descent and East Asian populations, some of the recurrent mutations differ even within the East Asian populations.

Diagnosis and Treatment of Lower Extremity Deep Vein Thrombosis: Korean Practice Guidelines

Lower extremity deep vein thrombosis is a serious medical condition that can result in death or major disability due to pulmonary embolism or post-thrombotic syndrome. Appropriate diagnosis and treatment are required to improve symptoms and salvage the affected limb. Early thrombus clearance rapidly resolves symptoms related to venous obstruction, restores valve function and reduces the incidence of post-thrombotic syndrome. Recently, endovascular treatment has been established as a standard method for early thrombus removal. However, there are a variety of views regarding the indications and procedures among medical institutions and operators. Therefore, we intend to provide evidence-based guidelines for diagnosis and treatment of lower extremity deep vein thrombosis by multidisciplinary consensus. These guidelines are the result of a close collaboration between interventional radiologists and vascular surgeons. The goals of these guidelines are to improve treatment, to serve as a guide to the clinician, and consequently to contribute to public health care.

Thrombophilia in Korean patients with arterial or venous thromboembolisms

Purpose

To determine the prevalence of thrombophilia in Korean patients with an arterial thromboembolism (ATE) or a venous thromboembolism (VTE), and to evaluate the characteristic of VTE in patients with thrombophilia.

Methods

Hospital records of 294 patients (228 with VTE, 66 with ATE) including two foreign ones (mean age, 51.4 years) who underwent thrombophilia testing between August 2006 and March 2015 were reviewed retrospectively. In general, such screening was performed according to the guidelines of the international consensus statement for VTE. Thrombophilia testing included evaluations of the factor V Leiden and prothrombin G20210A mutations, levels of proteins C and S and antithrombin, and antiphospholipid antibody syndrome (APLS).

Results

A factor V Leiden mutation was not found in the 292 Korean patients. A prothrombin G21210A mutation was investigated in 33 patients but none was found. Among 226 Korean patients with VTE, 130 demonstrated no thrombophilia and 55 patients did after exclusion of 41 patients without confirmatory test. The most common form was protein S deficiency (31 of 55, 56%) followed by protein C deficiency, antithrombin deficiency, and APLS. When comparing patients with a VTE or deep vein thrombosis (DVT) according to the presence of thrombophilia, thrombophilia was associated with younger age (P = 0.001 for VTE; P < 0.001 for DVT) and a family history (P < 0.001 for VTE and DVT).

Conclusion

We did not find any factor V Leiden mutation in Korean subjects at high risk for thrombophilia. Therefore, this testing is not warranted. Thrombophilia was associated with VTE in younger age and a family history.

Ethnic diversity in the genetics of venous thromboembolism

Genetic susceptibility is considered as a crucial factor for the development of venous thromboembolism (VTE). Epidemiologic and genetic studies have revealed clear disparities in the incidence of VTE and the distribution of genetic factors for VTE in populations stratified by ethnicity worldwide. While gain-of-function polymorphisms in the procoagulant genes are common inherited factors in European-origin populations, the most prevalent molecular basis for venous thrombosis in Asians is confirmed to be dysfunctional variants in the anticoagulant genes. With the breakthrough of genomic technologies, a set of novel common alleles and rare mutations associated with VTE have also been identified, in different ethnic groups. Several putative pathways contributing to the pathogenesis of thrombophilia in populations of African-ancestry are largely unknown, as current knowledge of hereditary and acquired risk factors do not fully explain the highest risk of VTE in Black groups. In-depth studies across diverse ethnic populations are needed to unravel the whole genetics of VTE, which will help developing individual risk prediction models and strategies to minimise VTE in all populations.

Prenatal genetic testing for familial severe congenital protein C deficiency

Severe congenital protein C (PC) deficiency is an autosomal recessive hereditary thrombophilia caused by mutations in PROC. The case manifested severe purpura fulminans, intracranial thrombosis or hemorrhage within 4 days after birth, resulting in blindness. We report the identification of inherited compound heterozygous mutations, including a novel nonsense mutation in PROC, and a prenatal genetic test for a subsequent pregnancy. Prenatal diagnosis may facilitate preemptive and radical therapy for severe PC deficiency.

A novel nonsense mutation Tyr301* of PROS1 causing protein S deficiency

Hereditary protein S deficiency is one of the natural anticoagulant deficiency causing thrombophilia. Protein S deficiency is caused by a mutation in the PROS1 gene on 3q11.2 and is typically inherited in an autosomal dominant manner. We herein describe a Korean man with protein S deficiency from a novel nonsense mutation of PROS1. The patient was a 47-year-old man with deep-vein thrombosis. No relevant family history was documented. Coagulation test results included a significantly decreased protein S activity at 30%. Molecular genetic analysis targeting PROS1 on suspicion of hereditary protein S deficiency revealed that he was heterozygous for a novel transversion mutation, c.903C>G, in the exon 9 of PROS1. The mutation was predicted to result in premature termination at the codon 301 in the laminin G-type domain (p.Tyr301) of the protein (nonsense mutation). According to a review of the literature and database, the mutation described herein is the first substitution mutation affecting the codon 301 of PROS1.

Thromboembolism in pregnancy: challenges and controversies in the prevention of pregnancy-associated venous thromboembolism and management of anticoagulation in women with mechanical prosthetic heart valves

Thromboembolism in pregnancy is an important clinical issue. Despite identification of maternal and pregnancy-specific risk factors for development of pregnancy-associated venous thromboembolism, limited data are available to inform on optimal approaches for prevention. The relatively low overall prevalence of pregnancy-associated venous thromboembolism has prompted debate about the validity of recommendations, which are mainly based on expert opinion, and have resulted in an increased use of pharmacological thromboprophylaxis in pregnancy and postpartum. A pragmatic approach is required in the absence of more robust data. Anticoagulation management of pregnant women with mechanical prosthetic heart valves is particularly challenging. Continuation of therapeutic anticoagulation during pregnancy is essential to prevent valve thrombosis. Warfarin, the most effective anticoagulant, is associated with adverse fetal outcomes, including embryopathy and stillbirth. Fetal outcome is improved with therapeutic-dose low-molecular-weight heparin, but there may be more thromboembolic complications. More intensive anticoagulation, targeting higher trough anti-Xa levels, may reduce the risk of valve thrombosis.