Normal ranges and genetic variants of antithrombin, protein C and protein S in the general Chinese population. Results of the Chinese Hemostasis Investigation on Natural Anticoagulants Study I Group

The Association between Disseminated Intravascular Coagulation Profiles and Neurologic Outcome in Patients with In-Hospital Cardiac Arrest

Background

The relationship between disseminated intravascular coagulation (DIC) profiles and survival or neurological outcomes in out-of-hospital cardiac arrest (OHCA) patients is well known. In contrast, the relationship between DIC profiles and neurological outcomes in patients with in-hospital cardiac arrest (IHCA) remains unclear. This study sought to examine the correlation between DIC profiles and neurological outcomes in IHCA patients.

Methods

A retrospective observational study was conducted on comatose adult IHCA patients treated with targeted temperature management between January 2017 and December 2022. DIC profiles were used to calculate the DIC score, and were measured immediately after the return of spontaneous circulation (ROSC). The primary endpoint was a poor neurological outcome at six months, defined by cerebral performance in categories 3, 4, or 5. Multivariate analysis was used to evaluate the association between DIC profiles and poor neurological outcomes.

Results

The study included 136 patients, of which 107 (78.7%) patients demonstrated poor neurological outcomes. These patients had higher fibrinogen (3.2 g/L vs. 2.3 g/L) and fibrin degradation product levels (50.7 mg/L vs. 30.1 mg/L) and lower anti-thrombin III (ATIII) levels (65.7% vs. 82.3%). The DIC score did not differ between the good and poor outcome groups. In multivariable analysis, fibrinogen (odds ratio [OR], 1.009; 95% confidence intervals [CI], 1.003-1.016) and ATIII levels (OR, 0.965; 95% CI, 0.942-0.989) were independently associated with poor neurological outcomes.

Conclusions

Decreased fibrinogen and ATIII levels after ROSC were an independent risk factor for unfavorable neurological outcomes in IHCA. The DIC score is unlikely to play a significant role in IHCA prognosis in contrast to OHCA.

Acute liver failure as initial presentation in a Chinese patient with Budd-Chiari syndrome due to protein C deficiency: A case report and literature review

Acute liver failure is an uncommon presentation in the clinic. Common causes for acute liver failure include viral hepatitis and drug-related hepatotoxicity. However, acute liver failure due to Budd-Chiari syndrome is rare. This case highlights the importance of necessary constrast-enhanced imaging studies to rule out vascular etiologies of acute liver failure, in addition to common causes like viral or drug-induced hepatic failure. We present a case of a male Chinese patient who presented with nausea, vomiting, fatigue, and fever after eating a large amount of fatty food. Six days after hospitalization, the patient developed acute liver failure and hepatic encephalopathy. Contrast-enhanced computerized tomography and ultrasound examinations revealed thromboses in the hepatic veins and inferior vena cava. Further testing also showed decreased protein C activity. Therefore, a diagnosis of Budd-Chiari syndrome secondary to protein C deficiency was made. He received supportive care and a transjugular intrahepatic portal shunt. Hepatic function, coagulation panel results, and clinical presentations gradually returned to normal. Budd-Chiari syndrome from protein C deficiency could be a rare but valid cause of acute liver failure in Chinese patients.

Thrombophilia Screening: Not So Straightforward

Although inherited thrombophilias are lifelong risk factors for a first thrombotic episode, progression to thrombosis is multifactorial and not all individuals with inherited thrombophilia develop thrombosis in their lifetimes. Consequently, indiscriminate screening in patients with idiopathic thrombosis is not recommended, since presence of a thrombophilia does not necessarily predict recurrence or influence management, and testing should be selective. It follows that a decision to undertake laboratory detection of thrombophilia should be aligned with a concerted effort to identify any significant abnormalities, because it will inform patient management. Deficiencies of antithrombin and protein C are rare and usually determined using phenotypic assays assessing biological activities, whereas protein S deficiency (also rare) is commonly detected with antigenic assays for the free form of protein S since available activity assays are considered to lack specificity. In each case, no single phenotypic assay is capable of detecting every deficiency, because the various mutations express different molecular characteristics, rendering thrombophilia screening repertoires employing one assay per potential deficiency, of limited effectiveness. Activated protein C resistance (APCR) is more common than discrete deficiencies of antithrombin, protein C, and protein S and also often detected initially with phenotypic assays; however, some centres perform only genetic analysis for factor V Leiden, as this is responsible for most cases of hereditary APCR, accepting that acquired APCR and rare F5 mutations conferring APCR will go undetected if only factor V Leiden is evaluated. All phenotypic assays have interferences and limitations, which must be factored into decisions about if, and when, to test, and be given consideration in the laboratory during assay performance and interpretation. This review looks in detail at performance and limitations of routine phenotypic thrombophilia assays.

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

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

Digenic Inheritance of PROC and SERPINC1 Mutations Contributes to Multiple Sites Venous Thrombosis

Venous thromboembolism (VTE) represents a worldwide health challenge, impacting millions of people each year. The genesis of venous thrombosis is influenced in part by genetic components. Hereditary thrombosis is described as a genetically determined susceptibility to VTE. In the present study, a male patient was referred to our department presenting with multiple venous thrombosis events in different locations. Given a lack of identifiable risk factors, we aimed to investigate the possible genetic factor underlying venous thrombosis. Whole-exome sequencing was employed to examine genes linked to inherited thrombophilia in the proband. Putative variants were subsequently confirmed through Sanger sequencing within the family. The proband was identified as carrying two genetic mutations. One is the novel c.400G > C (p.E134Q) mutation affecting the final nucleotide of exon 5 in the PROC gene, potentially impacting splicing. The other is a previously reported heterozygous nonsense variant c.1016G > A (p.W339X) in the SERPINC1 gene. The proband inherited the former from her mother and the latter from her father. The presence of digenic inheritance in the patient reflects the complex phenotype of venous thrombosis and demonstrates the significance of an unbiased approach to detect pathogenic variants, especially in patients with a high risk of hereditary thrombosis.

COVID-19-associated coagulopathy and acute kidney injury in critically ill patients

OBJECTIVE

The incidence of thrombotic events and acute kidney injury is high in critically ill patients with COVID-19. We aimed to evaluate and compare the coagulation profiles of patients with COVID-19 developing acute kidney injury versus those who did not, during their intensive care unit stay.

METHODS

Conventional coagulation and platelet function tests, fibrinolysis, endogenous inhibitors of coagulation tests, and rotational thromboelastometry were conducted on days 0, 1, 3, 7, and 14 following intensive care unit admission.

RESULTS

Out of 30 patients included, 13 (43.4%) met the criteria for acute kidney injury. Comparing both groups, patients with acute kidney injury were older: 73 (60-84) versus 54 (47-64) years, p=0.027, and had a lower baseline glomerular filtration rate: 70 (51-81) versus 93 (83-106) mL/min/1.73m2, p=0.004. On day 1, D-dimer and fibrinogen levels were elevated but similar between groups: 1780 (1319-5517) versus 1794 (726-2324) ng/mL, p=0.145 and 608 (550-700) versus 642 (469-722) g/dL, p=0.95, respectively. Rotational thromboelastometry data were also similar between groups. However, antithrombin activity and protein C levels were lower in patients who developed acute kidney injury: 82 (75-92) versus 98 (90-116), p=0.028 and 70 (52-82) versus 88 (78-101) µ/mL, p=0.038, respectively. Mean protein C levels were lower in the group with acute kidney injury across multiple time points during their stay in the intensive care unit.

CONCLUSION

Critically ill patients experiencing acute kidney injury exhibited lower endogenous anticoagulant levels. Further studies are needed to understand the role of natural anticoagulants in the pathophysiology of acute kidney injury within this population.

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.

Genomic Analysis of Thrombophilia Variants in the General Population for the Creation of an Effective Preoperative Screening Tool

BACKGROUND

 The loss of a free flap in reconstructive microsurgery is a devastating complication in both the intraoperative and postoperative setting. Previous research has identified a variety of genetic polymorphisms that induce a hypercoagulable state and predispose patients to clot formation and subsequent free flap loss. We aim to review the risks of performing microsurgery on patients who are genetically predisposed to hypercoagulability, as well as identify options, for preoperative screening of inherited thrombophilia.

METHODS

 A thorough literature review was conducted with an online database. A total of 30 studies were reviewed to identify genetic polymorphisms that cause inherited thrombophilia. Through manual review of the literature, a table was created that included thrombotic risk factors and their associated genetic polymorphisms. If the information was available, prevalence for each thrombotic risk was also reported.

RESULTS

 Overall, 18 thrombotic risk factors that contribute to hereditary thrombophilia were identified and linked with specific genes and/or genetic polymorphisms. In studies that did not look at particular ethnic groups, 13 unique thrombotic risk factors were identified. In studies that examined specific ethnic groups exclusively, 12 thrombotic risk factors were identified and related to their respective gene or group of genes. Five of the 18 thrombotic risk factors identified were associated with increased risks of both venous and arterial thrombosis. The remainder of the thrombotic risk factors was associated with increased risk of venous thrombosis exclusively.

CONCLUSION

 The use of genetic screening tests for hereditary thrombophilia in the preoperative setting can serve as an effective preventative measure against postoperative thrombosis. Further exploration of thrombotic risk factors and their related genetic polymorphisms are important steps in reducing postoperative free flap loss.

Primary myelofibrosis with thrombophilia as first symptom combined with thalassemia and Gilbert syndrome: A case report

BACKGROUND

A 46-year-old Han man first had sigmoid sinus and transverse sinus venous thrombosis at the age of 42. At the age of 44, he once again developed thrombosis. Genetic testing showed heterozygous SERPINC1 mutation, bone marrow biopsy showed fibrosis grade 1 (MF-1), and JAK2 V617F mutation was positive, accompanied by UGT1A1 mutation and β-thalassemia gene mutation.

CASE SUMMARY

A 46-year-old Han man was first found to have sigmoid sinus and transverse sinus venous thrombosis at the age of 42 but had no individual or family thrombosis history, and he had been regularly taking warfarin anticoagulant therapy for a long period of time. At the age of 44, venous thrombosis reappeared in parts of the intrahepatic vein, main portal vein, splenic vein, and superior mesenteric vein, and his spleen was obviously enlarged. He had a history of jaundice for many years, and genetic testing revealed that he carried a heterozygous SERPINC1 mutation. Bone marrow biopsy showed multifocal fibrous tissue hyperplasia among trabeculae and focal fibrosis. He was positive for the JAK2 V617F mutation. At the same time, UGT1A1 and β-thalassemia gene mutations existed, and a SERPINC1 mutation and UGT1A1 mutation were both found in his parents.

CONCLUSION

The patient in this case had thrombophilia as the primary symptom, JAK2V617-positive myeloproliferative neoplasm (MPN) was the main potential cause, and hereditary AT-III deficiency may have been one of multiple secondary causes. It remains to be determined whether UGT1A1 and β-thalassemia gene mutations are related to thrombophilia. However, the clinical features of MPN in this patient were hidden, and the relevant clinical features of coexisting thalassemia and hereditary Gilbert syndrome, reported here for the first time domestically and abroad, were complicating factors, causing great difficulties for a clear diagnosis. Thus, when thrombophilia has been determined, it is necessary to screen the relevant latent problems overall. When the clinical features cannot be perfectly explained by one etiology, a relevant comprehensive examination should also be initiated from the perspective of multiple etiologies.

Reference interval of antithrombin, protein C, and protein S activities in healthy adults in Iran, the effect of age, sex, oral contraceptive intake, and menopause

BACKGROUND

Antithrombin (AT), protein C (PC), and protein S (PS) are natural anticoagulant proteins that deficiency in each of them is associated with an increased risk of venous thromboembolism.The overlapping of plasma levels of AT, PC, and PS between healthy individuals and heterozygote carriers poses significant challenges in precise diagnosis. This study aimed to evaluate the effect of most influencing variables on plasma levels of these proteins and propose specific reference intervals to improve the interpretation of the laboratory results.

METHODS

This study was conducted on 1464 individuals who were referred to Massoud medical laboratory, Tehran, Iran, from 2019 to 2020. AT and PC were measured through chromogenic assay and PS plasma level with the clot-based assay. A multivariable linear regression model was performed to evaluate the effect of sex, age, oral contraceptive (OCP) intake, and menopause state. Normal deviate z value was used for different subgroups to justify the need for a separate reference interval.

RESULTS

1200 verified healthy individuals (434 males and 766 females), aged between 18 and 69 years were included in the study. The mean ± SD age of the participants was 39.78 ± 11.79 years. The age-related effects for AT were found in men. In females, increasing age was associated with a rise in AT, PC, and PS plasma levels. No sex difference was found in AT plasma level. OCP-taking is associated with a decrease in AT and an increase in PC plasma levels.

CONCLUSION

This is the largest study ever conducted on healthy individuals in the Iranian population, using specific reference interval results in accurate diagnosis of true AT, PC, and PS deficiency.

A case-report of two patients with hereditary protein S deficiency treated by rivaroxaban

: Hereditary protein S deficiency is an autosomal dominant disorder associated with a high risk of venous thromboembolism (VTE) and usually results from mutations of PROS1. Historically heparin and warfarin have been applied as recommended treatment of VTE. Recent researches showed that rivaroxaban provided more consistent and predictable anticoagulation than warfarin. However, it is unknown whether rivaroxaban is effective for the treatment of VTE in patients with thrombophilia, including protein S deficiency, due to lack of evidence. Here, we report two cases of recurrent VTE in two patients with hereditary protein S deficiency, owing to the same nonsense mutation in PROS1, which were successfully treated by rivaroxaban monotherapy.

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.

A Study of Congenital Protein C Deficiency With Infancy Onset of CADASIL in a Chinese Baby

OBJECTIVE

The main objectives of this article were to study a severe congenital protein C deficiency (PCD) in a patient with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and analyze the cause of this case.

MATERIALS AND METHODS

We had recorded clinical manifestations of the patient, laboratory tests, imaging studies, and gene sequencing of the PROC gene and NOTCH3 gene to study the disease in this family. We checked the change of NOTCH3 protein by immunohistochemistry.

RESULTS

Laboratory studies of the patient had revealed that his PC activity was 3%. Magnetic resonance imaging results showed hyperintense lesions in the cerebral white matter of the patient. PROC gene and NOTCH3 gene sequencing was performed among the family members. The patient was confirmed as homozygous for the (A-G)-12 at the transcription initiation site in the promoter region of the PROC gene and heterozygous mutation of the NOTCH3 gene. Immunohistochemical results showed that NOTCH3 protein was positive in the skin vascular smooth muscle of the patient.

CONCLUSIONS

We studied a rare case of an infat boy diagnosed with both congenital PCD and CADASIL; congenital PCD was attributable to a compound that was homozygous for (A-G)-12 at the transcription initiation site in the promoter region of the PROC gene, and CADASIL was caused by missense mutation in exon 24 of NOTCH3. He was a sporadic patient with congenital PCD and CADASIL; it maybe that the deficiency of protein C led to early onset of CADASIL. The gene sequencing of PROC gene and NOTCH3 gene may have important value for fertility guidance and prenatal diagnosis.

Protein C deficiency resulting from two mutations in PROC presenting with recurrent venous thromboembolism

Hereditary protein C (PC) deficiency is an autosomal dominant disorder associated with a high risk of venous thromboembolism (VTE). Here we report a case of inherited PC deficiency associated with recurrent deep venous thrombosis. Two mutations were revealed in PROC (c.1152C>G, p.N384K and c.1207G>T, p.G403W) by genetic testing. Results from this case suggest that the inherited PC deficiency due to the PROC mutations may cause recurrent VTE. Long-term anticoagulant therapy may be appropriate for these patients with recurrent VTE and hereditary PC deficiency.

Venous thromboembolism in Asia – an unrecognised and under-treated problem?

Venous thromboembolism (VTE) has been perceived for a long time to be less common in Asian populations, particularly in the Far East, than in Western populations. Generally, thromboprophylaxis is not implemented as frequently as it should be in high-risk patients. However, recent prospective studies undertaken in Asian countries have demonstrated higher rates of VTE after major surgery and in medical wards, approaching those observed in Western populations. Risk factors for VTE are not different in Asian patients from those of Western patients with the exception of thrombophilic mutations. Deficiencies of the natural anticoagulants (protein S, protein C, and antithrombin) are the predominant thrombophilias in Asia whereas factor V Leiden and prothrombin G20210A gene mutation are not found or rarely reported. Further large well-designed clinical studies are needed to evaluate the magnitude of the risk of VTE and the appropriate use of thromboprophylaxis in different clinical situations.

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.

Coagulation factors, anticoagulant proteins, and plasminogen in Mexican older adults

INTRODUCTION

Hemostasis protects upon the occurrence of vascular endothelial damage, with involving of different factors. The interaction of these factors in older adults is poorly known, and has been associated with different disorders. Therefore, we determined the activity of coagulation factors (CF), anticoagulant proteins (AP), and plasminogen (Plg), as well as the frequency of deficiencies of these proteins in a population of healthy Mexican older adults (OA).

METHODS

CF (I, II, V, VII, VIII, IX, X, and XI y XII), AP [protein C (PC), protein S (PS), and antithrombin (AT)], and Plg were determined from 244 plasma samples of OA using commercial kits in a coagulometer ACL Elite Pro.

RESULTS

A total of 139 women and 105 men were under study. They were divided into age range groups (50-59, 60-69, 70-79, and ˃80 years). Activity of CF, AP, and Plg was determined. Frequencies of CF, AP, and Plg activity values were obtained for each age group according to gender. Differences were found between both frequencies for each protein.

CONCLUSION

Significant differences were found, so it is recommended to establish reference values (RV) for the activity of fibrinogen and FX by decade and gender, FVII and FXII by gender, FII, FV, FVIII, PC, PS, and Plg by decade, whereas for FIX, FXI, and AT, they are not modified by age or gender, so the RV described for adult Mexican population can be used. It is important to integrate these results into established diagnostic algorithms, which can be taken into account to provide an accurate diagnosis and treatment for patients with suspected hemorrhagic or thrombotic processes, as well as suggest those habits that improve their quality of life, to maintain optimal health and prevent thrombotic and hemorrhagic events.

Bidirectional risk between venous thromboembolism and cancer in East Asian patients: synthesis of evidence from recent population-based epidemiological studies

BACKGROUND

Unprovoked (idiopathic) venous thromboembolism (VTE) with no obvious antecedent risk factors, is associated with a significant risk of subsequent occult cancer. Conversely, there is a heightened risk of VTE in cancer patients. This bidirectional risk can be estimated from population-based cohort studies conducted in East Asians.

METHODS

A literature search using medical subject heading terms and Boolean logic in PubMed and MedLine was performed in April 2017. Twenty-two papers reported from East Asia were retrieved for study and data synthesis. Proportional meta-analysis with a random-effects model was used to synthesize data with 95% confidence intervals (CIs) when appropriate.

RESULTS

Synthesis of data on VTE incidence in the East Asian population (I² = 76.2%) showed that pooled incidence was 20.3 (95% CI, 11.2-32) per 100,000 person-years. VTE incidence steadily increased with age. Unprovoked VTE accounted for 35% (95% CI, 24%-48%) of all cases of incident VTE (I² = 99.7%). The overall cancer risk was significantly higher (2.3-fold) in the VTE cohort than in comparators. Among the patients with unprovoked VTE, approximately 7% had a subsequent cancer diagnosis within 2 years of the first episode of idiopathic VTE. The risk of VTE recurrence was increased in cancer patients (adjusted odds ratio, 1.64; 95% CI, 1.26-1.99). VTE incidence was 9.9 per 1,000 person-years in cancer patients, particularly in liver, pancreas, and lung cancer patients.

CONCLUSION

Newly diagnosed VTE incidence is estimated at approximately 4,400 new cases annually in Taiwan and 7,100 in South Korea. Similar to the trend in VTE incidence among the general population, VTE risk in East Asian cancer patients is markedly lessened.

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.

A novel PROS1 mutation, c.74dupA, was identified in a protein S deficiency family

Protein S is a vitamin K-dependent plasma glycoprotein that acts as an anticoagulant, and its deficiency usually predisposes individuals to venous thromboembolism. Hereditary protein S deficiency is an autosomal dominant disorder caused by a PROS1 mutation. Herein, we described a novel PROS1 frameshift mutation, c.74dupA, in a hereditary protein S deficiency family. Interestingly, both of the proband and his mother carried the mutation and had a protein S deficiency, however, only the proband suffered a pulmonary embolism while his mother had no history of any thrombosis, suggesting that a triggering event might have been involved in the thrombus formation. Therefore, genetic testing of PROS1 appeared important for the early diagnosis of hereditary protein S deficiency, and it allowed the application of prophylactic interventions to prevent the incidence of severe thrombosis.

Risk indicators for venous thrombosis in first-degree relatives of patients with recurrent venous thromboembolism in Chinese

Having encountered several subjects with venous thromboembolism (VTE) in 1 family in which 1 proband has recurrent VTE (rVTE), we aimed to assess the risk of VTE in first-degree relatives, especially the children of individuals with rVTE, and to investigate the association of endothelial nitric oxide synthase (eNOS) G894T polymorphism between Chinese persons with rVTE and their offspring.We collected information about family histories and blood samples from 126 individuals with rVTE who had presented to our institute from 2003 to 2014, and 126 population-based controls and the first-degree relatives of subjects in these 2 groups. We tested blood samples for heritable thrombophilia and calculated odds ratios (ORs) and kappa coefficients.First-degree relatives of individuals with rVTE patients had a statistically significant risk of developing VTE (OR 2.62, 95% confidence interval [CI] 1.61-4.26, P < 0.001). For siblings, the OR was 2.72 (95% CI 1.56-4.73, P < .001). Moreover, for each year that the patient was older, the OR was 0.98 (95% CI 0.97-0.99, P = 0.03). One (11.2%) of the 9 individuals who had the same eNOS G894T polymorphism as their probands had a history of VTE, whereas none of the 17 relatives without the same polymorphism had developed VTE. The associations between patients and their children were statistically significant for VTE (kappa = 0.23, P < 0.001) and for eNOS G894T (kappa = 0.03, P = 0.04).In this case-controlled study, we demonstrated a higher risk of VTE among first-degree relatives of individuals with rVTE, especially in siblings of younger subjects with rVTE. We also found that eNOS G894T polymorphism may be a predictor of VTE in offspring of individuals with rVTE.

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.

Expression and Characterization of Gly-317 Variants of Factor IX Causing Variable Bleeding in Hemophilia B Patients

We recently identified two hemophilia B patients who carried Gly-317 to Arg (FIX-G317R) or Gly-317 to Glu (FIX-G317E) substitutions in their FIX gene. The former mutation caused severe and the latter moderate bleeding in afflicted patients. To understand the molecular basis for the variable clinical manifestation of Gly-317 mutations, we prepared recombinant G317R and G317E derivatives of FIX and compared their kinetic properties to those of recombinant wild-type FIX in appropriate assay systems. Both physiological activators, factor XIa and extrinsic Tenase (factor VIIa-tissue factor), activated both zymogen variants with an ∼1.5-fold elevated K(m); however, extrinsic Tenase activated FIX-G317E with an ∼2-fold improved k(cat). By contrast to zymogen activation, the catalytic activities of both FIXa-G317R and FIXa-G317E enzymes toward the natural substrate, factor X, were dramatically (>4 orders of magnitude) impaired, but their apparent affinity for interaction with factor VIIIa was only slightly (<2-fold) decreased. Further studies revealed that the reactivity of FIXa-G317R and FIXa-G317E with antithrombin has been impaired 10- and 13-fold, respectively, in the absence and 166- and 500-fold, respectively, in the presence of pentasaccharide. As expected, the clotting activities of FIX variants could not be measured by the aPTT assay. These results implicate a critical role for Gly-317 in maintaining normal catalytic function for FIX/FIXa in the clotting cascade. The results further suggest that improved k(cat) of FIX-G317E activation in the extrinsic pathway together with dramatically impaired reactivity of FIXa-G317E with antithrombin may account for the less severe bleeding phenotype of a hemophilia B patient carrying the FIX-G317E mutation.

Progress in research into the genes associated with venous thromboembolism

BACKGROUND

Venous thromboembolism (VTE), including both deep vein thrombosis (DVT) and pulmonary embolism (PE), is a common, lethal disorder that affects hospitalized and non-hospitalized patients. This study aimed to review the progress in the research into VTE.

DATA SOURCES

We reviewed the studies about VTE and verified different genetic polymoriphisms of VTE.

RESULTS

The pathogenesis of VTE involves hereditary and acquired factors. Many studies indicated that the disorder of coagulation and fibirnolytic system is of utmost importance to this disease. Genetic polymoriphism-related VTE demonstrated significant differences among geographies and ethnicities.

CONCLUSION

VTE has many risk factors, but genetic factors play an important role.

Childhood asthma is associated with polymorphic markers of PROC on 2q14 in addition to 17q21 locus

BACKGROUND

Childhood asthma is caused by both genetic and environmental factors. The first genomewide association study (GWAS) for asthma revealed putative candidates on nine chromosomal regions in Caucasians, with 17q21 locus being the most widely replicated one. However, there was no replication study for the other loci. This study investigated genetic associations between childhood asthma and autosomal single nucleotide polymorphisms (SNPs) on eight loci reported in the first GWAS among Hong Kong Chinese.

METHODS

510 asthmatic children and 510 non-allergic controls were recruited. 110 tagging SNPs selected based on r(2 ) ≥ 0.80 and minor allele frequency ≥0.05 for Han Chinese among all SNPs located 50-kb upstream and downstream of significant autosomal SNPs were genotyped by TaqMan allelic discrimination assays. Transcription factor binding of SNPs was determined by electrophoretic mobility shift assay (EMSA).

RESULTS

Asthma was significantly associated with SNPs on 17q21 and 2q14 loci. Twelve SNPs on 17q21 were associated with asthma, with rs6503527 being the most significant SNP. Five SNPs of protein C gene (PROC) on 2q14 were associated with asthma, with rs6755028 being the most significant SNP. Plasma protein C concentrations were higher in asthmatic patients than controls, and five PROC SNPs were associated with plasma protein C concentrations. EMSA showed specific differential binding of rs878461 to nuclear extracts from bronchial epithelial and hepatocarcinoma cell lines.

CONCLUSIONS

Our findings identify PROC on 2q14 as a novel candidate for childhood asthma and replicate the genetic association for 17q21 locus. Rs878461 of PROC may increase asthma susceptibility by altering transcription factor binding.

Protein C Thr315Ala variant results in gain of function but manifests as type II deficiency in diagnostic assays

Protein C (PC) is a vitamin K-dependent plasma glycoprotein, which upon activation by thrombin in complex with thrombomodulin (TM), regulates the coagulation cascade through a feedback loop inhibition mechanism. PC deficiency is associated with an increased risk of venous thromboembolism (VTE). A recent cohort study aimed at establishing a normal PC range identified a healthy PC-deficient subject whose PC antigen level of 65% and activity levels of 50% (chromogenic assay) and 36% (clotting assay) were markedly low. The proband has a negative family history of VTE. Genetic analysis revealed the proband has a heterozygous missense mutation in which Thr-315 of the PC heavy chain has been substituted with Ala. We expressed this mutant in HEK-293 cells and purified it to homogeneity. A similar decrease in both anticoagulant and anti-inflammatory activities of the activated protein C mutant was observed in plasma- and cell-based assays. Interestingly, we discovered if functional assays were coupled to PC activation by the thrombin-TM complex, the variant exhibits improved activities in all assays. Sequence analysis revealed Thr-315 is a consensus N-linked glycosylation site for Asn-313 and that its elimination significantly (∼four- to fivefold) improves the maximum velocity of PC activation by the thrombin-TM complex, explaining the basis for the proband's negative VTE pedigree.

TAM receptor signaling in immune homeostasis

The TAM receptor tyrosine kinases (RTKs)-TYRO3, AXL, and MERTK-together with their cognate agonists GAS6 and PROS1 play an essential role in the resolution of inflammation. Deficiencies in TAM signaling have been associated with chronic inflammatory and autoimmune diseases. Three processes regulated by TAM signaling may contribute, either independently or collectively, to immune homeostasis: the negative regulation of the innate immune response, the phagocytosis of apoptotic cells, and the restoration of vascular integrity. Recent studies have also revealed the function of TAMs in infectious diseases and cancer. Here, we review the important milestones in the discovery of these RTKs and their ligands and the studies that underscore the functional importance of this signaling pathway in physiological immune settings and disease.

Dysfunction of protein C anticoagulant system, main genetic risk factor for venous thromboembolism in northeast Asians

Venous thromboembolism (VTE) is a life threatening medical disorder worldwide. A great deal of evidence suggests that prevalence of VTE varies significantly among ethnic populations, with consistently lower incidence found in Asians. While the distribution of genetic risk factors may vary among races, genetic risk factors can play a major role among individuals with different genetic backgrounds. Two clinically evaluated low-frequency genetic mutations that predispose to VTE--the factor V Leiden mutation and prothrombin G20210A mutation--are found predominantly in Caucasians, and virtually never in Asians. The findings of a recent genetic study of VTE in northeast Asians, which greatly advanced our knowledge in this area, indicate that the most frequent genetic risk factors for VTE in northeast Asians can be attributed to a dysfunction of the protein C anticoagulant system. Several low-frequency genetic mutations, PROS1 p.Lys196Glu in Japanese and PROC p.Arg189Trp and p.Lys193del in Chinese, are significantly associated with increased risk for VTE, with odds ratio more than 2 through the reduced protein C anticoagulant activity. Construction of a multifactorial model based on the genetic risk factors in the protein C anticoagulant system could facilitate genetic counseling for VTE risk in these populations. The influence of prevalent genetic mutations on the risk of VTE should be further investigated in Asian countries.

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.

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

Hereditary natural anticoagulant deficiencies are the major cause of genetic thrombophilia in Asia. Given the growing acknowledgment of the risk of venous thromboembolism in Asian populations, we investigated the frequency and mutation spectrums of natural anticoagulant deficiency in Korea. The group of patients consisted of consecutive patients with venous thromboembolism screened for thrombophilia. Genetic tests were performed on suspicion of natural anticoagulant deficiency. For the population group, >3,000 individuals were screened from routine check-ups, and those with a low level (<1(st) percentile) of natural anticoagulant underwent genetic tests. Mutations were detected by direct sequencing of PROC, PROS1, and SERPINC1, followed by additional multiplex ligation-dependent probe amplification for PROS1 and SERPINC1 for dosage mutations. Among 500 patients screened, 127 were suspected of having a natural anticoagulant deficiency, and this was genetically confirmed in 71: protein C deficiency in 36 (50.7%), antithrombin deficiency in 21 (29.6%), and protein S deficiency in 14 (19.7%). Among 3,129 individuals from the population who were screened, the frequency of natural anticoagulant deficiency was ~1.0%: antithrombin deficiency 0.49%, protein C deficiency 0.35%, and protein S deficiency 0.16%. Two PROC mutations causing type I protein C deficiency were prevalent (Arg211Trp and Met406Ile in patients and Arg211Trp in the population). Two SERPINC1 mutations causing type II antithrombin deficiency, Arg79Cys and Ser158Pro, were prevalent in the population group. This is the first study on the genetic epidemiology of natural anticoagulant deficiencies in Korea. The results demonstrated that the frequencies and spectrum of mutations underlying genetic thrombophilia in Korea are different not only from those in Caucasians but also those in other Asian populations.

Molecular basis of protein S deficiency in China

Protein S (ProS) is a physiological inhibitor of coagulation with an important function in the down-regulation of thrombin generation. ProS deficiency is a major risk factor for venous thrombosis. This study enrolled 40 ProS-deficient probands to investigate the molecular basis of hereditary ProS deficiency in Chinese patients. A mutation analysis was performed by resequencing the PROS1 gene. Large deletions were identified by multiplex ligation-dependent probe amplification (MLPA) analysis. A total of 20 different mutations, including 15 novel mutations, were identified in 21 of the 40 index probands. Small mutations were detected in 18 (45.0%) probands, and large deletions were found in 3 (7.5%) probands, leaving 19 (47.5%) patients without causative variants. To evaluate the functional consequences of 2 novel missense variants, ex vivo thrombin-generation assays, bioinformatics tools, and in vitro expression studies were employed. The p.Asn365Lys ProS variant was found to have moderately impaired secretion and reduced activated protein C cofactor activity. In contrast, the p.Pro410His mutant appeared to have severely impaired secretion but full anticoagulant activity. This study is the largest investigation of ProS deficiency in China and the first investigation of the influence of Type I ProS missense mutations on the global level of coagulation function. The p.K196E mutation, which is common in the neighboring Japanese population, was not found in our Chinese population, and null mutations were common in our Chinese population but not common in Japan. Further genetic analysis is warranted to understand the causes of ProS deficiency in patients without a genetic explanation.

Deficiency of antithrombin and protein C gene in 202 Chinese venous thromboembolism patients

INTRODUCTION

Antithrombin and protein C gene deficiencies are commonly inherited risk factors for VTE patients. We aim to investigate the deficiency of these two gene in 202 Chinese patients with venous thromboembolism (VTE).

METHODS

Antithrombin activity (AT: A) and protein C activity (PC: A) were measured in 202 VTE patients, and for those with unexplainable low results, PCR and direct sequencing of the related genes were carried out.

RESULTS

Deficiency levels of antithrombin and protein C gene were found to be 2% and 8%, respectively. AT or PC hereditary deficiency can be found in 10% patients with VTE.

CONCLUSION

Protein C gene deficiency might be more prevalent than AT gene deficiency in Chinese VTE patients. Functional assay combined with genetic analysis is useful in the diagnosis of inherited defects in VTE patients.

Molecular basis and thrombotic manifestations of antithrombin deficiency in 15 unrelated Chinese patients

INTRODUCTION

Antithrombin (AT) deficiency is associated with an increasing risk of thrombosis.

MATERIALS AND METHODS

15 unrelated patients with AT deficiency defined by thrombophilic assays were recruited and detailed clinical information about patients, focusing on the personal and family history of thromboembolism (TE), were recorded. Mutation analysis was performed by direct sequencing of an AT gene (SERPINC1) in the patients and their family members.

RESULTS

A total of 15 heterozygous causative mutations, each being identified in one family, were identified. Five mutations (33.3%) were reported here for the first time, including three null mutations (Ser36X, Lys70X and Try307X) and two missense mutations (Phe123Cys and Leu340Phe) probably impairing the structural integrity and stability of protein based on the AT structural analysis. Of the 15 patients, 33.3% (5/15) had additional risk factors and only one patient presented with additional genetic alteration causing an early onset of thrombosis. Fourteen patients (93.9%) suffered from multisite recurrent thrombotic episodes after a first episode of thrombosis. 93.3% of the patients experienced deep vein thrombosis (DVT) and 40.0% presented with mesenteric venous thrombosis (MVT). In addition, both venous and arterial thrombosis was present in two unrelated patients. 51.0% subjects with AT deficiency in the 15 unrelated pedigrees experienced TE events.

CONCLUSIONS

Prophylactic anticoagulation may be suggested in AT-deficient patients to avoid the recurrent and multisite thrombosis. The association of primary MVT and AT deficiency is highlighted.

Expression and functional characterisation of natural R147W and K150del variants of protein C in the Chinese population

Protein C is a vitamin K-dependent serine protease zymogen in plasma which upon activation to activated protein C (APC) by thrombin down-regulates the clotting cascade by limited proteolysis of the procoagulant cofactors Va and VIIIa. In addition to its anticoagulant activity, APC also exhibits potent cytoprotective and anti-inflammatory activities. While the anticoagulant activity of APC is enhanced by the cofactor function of protein S on membrane phospholipids, the cytoprotective intracellular signalling activity of APC requires complex formation with endothelial protein C receptor (EPCR) expressed on the vascular endothelium. Two natural variants of APC [Arg-147 to Trp substitution (R147W) and Lys-150 deletion (K150del)] have been identified in the Chinese population as hotspot mutants occurring with high frequencies of 27.8% and 13.9%, respectively, among 36 protein C-deficient subjects. The affected individuals exhibit variable thrombotic tendencies. To understand the underlying cause of the thrombotic phenotype in these patients, we expressed these two protein C variants in mammalian cells and characterised their anticoagulant and anti-inflammatory properties using established in vitro and cellular assays. Our results suggest that both R147W and K150del variants have normal amidolytic and proteolytic activities in the absence of cofactors. However, the R147W mutant exhibits ~3 times lower affinity for binding to EPCR and the K150del variant has ~2-3-fold impaired anticoagulant activity in the presence of protein S. These results provide some insight into the possible pathogenic mechanism of protein C deficiency in Chinese patients carrying these mutations.

Genetic background analysis of protein C deficiency demonstrates a recurrent mutation associated with venous thrombosis in Chinese population

Background

Protein C (PC) is one of the most important physiological inhibitors of coagulation proteases. Hereditary PC deficiency causes a predisposition to venous thrombosis (VT). The genetic characteristics of PC deficiency in the Chinese population remain unknown.

Methods

Thirty-four unrelated probands diagnosed with hereditary PC deficiency were investigated. PC activity and antigen levels were measured. Mutation analysis was performed by sequencing the PROC gene. In silico analyses, including PolyPhen-2, SIFT, multiple sequence alignment, splicing prediction, and protein molecular modeling were performed to predict the consequences of each variant identified. One recurrent mutation and its relative risk for thrombosis in relatives were analyzed in 11 families. The recurrent mutation was subsequently detected in a case (VT patients)-control study, and the adjusted odds ratio (OR) for VT risk was calculated by logistic regression analysis.

Results

A total of 18 different mutations, including 12 novel variants, were identified. One common mutation, PROC c.565C>T (rs146922325:C>T), was found in 17 of the 34 probands. The family study showed that first-degree relatives bearing this variant had an 8.8-fold (95%CI = 1.1–71.6) increased risk of venous thrombosis. The case-control (1003 vs. 1031) study identified this mutation in 5.88% patients and in 0.87% controls, respectively. The mutant allele conferred a high predisposition to venous thrombosis (adjusted OR = 7.34, 95%CI = 3.61–14.94). The plasma PC activity and antigen levels in heterozygotes were 51.73±6.92 U/dl and 75.17±4.84 U/dl, respectively.

Conclusions

This is the first study on the genetic background of PC deficiency in the Chinese population. The PROC c.565C>T mutation is the most frequent cause of PC deficiency as well as a prevalent risk factor for VT in Chinese individuals. The inclusion of this variant in routine thrombophilic detection may improve the diagnosis and prevention of venous thrombosis.