Clinical Study On Related Risk Factors Of VTE And Molecular Mechanism Of Hereditary AT Deficiency Leading To Venous Thrombosis

Section 1 Clinical Study on Related Risk Factors of Venous Thromboembolism1.Objective: Analyze the clinical features and risk factors of venous thrombosis in inpatients.2.Methods: The demographic characteristics,related genetic and acquired risk factors of patients with venous thromboembolism(VTE)diagnosed in our hospital from 2016 to 2017 were analyzed retrospectively.The activity of antithrombin(AT)and protein C(PC)were measured by developing substrate method,and the activity of protein S(PS)was measured by coagulation method.Second generation gene sequencing was performed in some patients.The SPSS software and chi-square test were used to compare and analyze,and it is deemed as there was the statistical significance(P<0.05).3.Result: A total of 198 patients with VTE were collected at a median age of 61(14 to 92 years old),with a male and female ratio of 1.3 to 1.1.Among them,175 cases were first diagnosed,accounting for 88.4%.There were 23 recurrent cases,accounting for 11.6%.The age of the patients was mainly 61-70 years old,the onset age of male patients peaked at 51~60,witha median age of 59 years old.The onset age of female patients peaked at 61~70,with a median age of 62 years old.There was no significant difference in age distribution ratio between male and female patients.The most common site of VTE was thelower extremity DVT(68.7%),in which the left lower extremity was more common than the right lower extremity,accounting for 58.1% of the lower extremity DVT,which was related to the physiological anatomy position of the left common iliac vein.The production of VTE is influenced by many factors,and the main acquired risk factors were age lager than 70 years old(35.4%),braking/bed rest(24.7%),malignant tumor(21.2%),and operation/trauma(20.1%),and 2 or more acquired risk factors accounting for 79.6%in thisresearch.In 104 patients,the activity of PC,PS,and AT was tested in peripheral blood and liver diseases were excluded.Thirty-one patients with VTE were found to be deficient in anticoagulant.The results showed that AT deficiency was 11.5%,PS deficiency was 10.6% and PC was lack of 7.2%.The incidence of genetic and acquired risk factors was 61.3%.In some patients with VTE,the homocysteine,anticardiolipin antibody(ACA)and anti ?-GP1 antibody were significantly higher than those of non VTE patients when the patients found none of these common risk factors.It was suggested that the high homotypic cysteamine and anti-phospholipid antibody were also the risk factors for thrombosis.In the 3 patients with younger age(< 40 years old),recurrent thrombus,with no obvious acquired risk factors,the second-generation gene sequencing revealed that the PS and AT gene mutation resulted in decreased activity.4.Conclusion: Lower extremity DVT is the most common risk factor of VTE in inpatients,the age of onset is on 61 to 70 years old.The main genetic risk factors are the congenital deficiency of PC,PS,and AT,and the more common acquired risk factors are age larger than 70,surgical trauma,malignant tumor and so on.In addition,high homotypic cysteamine and anti-phospholipid antibodies are also the risk factors for VTE.The occurrence of VTE is the result of many factors,and the risk of VTE will increase when there are multiple risk factors.Exploring the risk factors of thrombosis in VTE patients can provide important basis for the application of clinical anticoagulant therapy.Section 2 Molecular Research Mechanism of Hereditary Antithrombin Deficiency Leading to Venous ThrombosisAntithrombin(AT)is one of the most important anticoagulants in human body.It is a glycoprotein secreted by hepatocytes with a relative molecular weight of 58.2 KD,belonging to the superfamily of serine proteinase inhibitor(SERPIN).The anticoagulant balance was maintained by inhibiting the activities of thrombin and the activated coagulation factor IX,X,XI and XII serine proteases,and the effect accounted for about 70% of the total anticoagulant activity.For a long time,basic and clinical studies have confirmed that AT deficiency is one of the genetic risk factors of thrombotic disease,especially in Asian population.The thrombosis will be caused when the quantity or quality of anticoagulant protein are defective.Hereditary antithrombin deficiency is caused by AT gene mutation,which is an autosomal dominant genetic rule,most of which is accompanied by family history.The main manifestation of the proband is the deep venous thrombosis or pulmonary embolism of the lower extremities which cannot be explained.The clinical manifestations of the patients with hereditary antithrombin deficiency were with a great individual difference.In this group,the main causes of the two proband patients were the repeated venous thrombosis of lower extremity and cerebral venous sinus thrombosis of unknown cause,respectively.The results of laboratory examination of proband in pedigree B were consistent with those of his father(using developing substrate method to test AT:A and other anticoagulant indexes,respectively),but the proband showed cerebral venous sinus thrombosis,and his father had a history of lower extremity thrombosis.PCR and nucleic acid sequencing methods were used to amplify and sequentially analyze the 7 exons and their ancepsintrons of the probands and other members of their families.The results showed that one case was a missense mutation caused by point mutation.In the other case,the deletion of 10 bases resulted in the mutation of reading frame shift,which resulted in the emergence of stop codon,Y198 N and R229 X,both of which were reported for the first time in the world.Two cases of hereditary antithrombin deficiency were not tested for antigens,but the proband a point mutation may be type II mutation,the proband b-base deletion may lead to the possibility of frame shift mutation to type I mutation.By clinical manifestation,family analysis and gene sequencing,it was confirmed that gene mutation in 2 patients with hereditary antithrombin deficiency resulted in the decrease of plasma antithrombin content or activity,which was the molecular mechanism leading to venous thromboembolism.The molecular characteristics of AT mutation may provide important information for studying the relationship between the structure and function of antithrombin proteins.