The Clinical Analyses Of Patients With Thrombotic Thrombocytopenic Purpura And The Molecular Mechanisms Of Antithrombin Gene Mutations In Hereditary Antithrombin Deficiency

ObjectiveThrombotic thrombocytopenic purpura (TTP),a case of thrombotic microangiopathy (TMA), is aclinical acute severe, once was a high mortality. With the discovery and cloning of the von Willebrandfactor-cleaving protease (ADAMTS13), so that we have a more indepth understanding of thepathogenesis of TTP. The clinical application of plasma exchange as an the TTP treatment,the diseasemortality has decreased from90%to10%-20%. Comprehensive analysis the patients of TTP withclinical characteristics, treatment strategies and outcome-depth understanding of the occurrence of thedisease, the development process and prognosis, help to improve the level of clinical diagnosis andtreatment of TTP and reduce mortality and relapse prevention.MethodsWe retrospectively analyzed the etiology、clinical manifestations、laboratory tests、treatment andoutcome of the data of the60TTP patients who registered and confirmed in our laboratory fromJan.2007to Nov.2012. T-test was used to compare effective group with death group in some relatedvariables. Relevant statistical analyzes were performed using GraphPad Prism5software, P <0.05wasstatistically significant.Results60TTP patients are made up with9cases of hereditary TTP and51cases of acquired TTP.9cases (15%)with hereditary TTP patients were induced by pregnancy or childbirth;51cases (85%)of patientswith acquired TTP are all idiopathic TTP. Of these,31cases (51.7%) have unknown etiology,10patients (16.7%) associated with immune system disorders,6patients (10%) associated with infection,4cases (6.7%) related to pregnancy or childbirth.. We statisticaly analyzed the60cases of TTP patientswith clinical manifestations, of which only18cases (30%) have typical pentalogy of TTP(thrombocytopenia, microangiopathic hemolytic anemia, neurologic abnormalities, fever and renalabnormalities)，22patients(36.7%) have4symptoms,15patients (25%) have3symptoms,5patients(8.3%) have2symptoms of typical pentalogy of TTP; From other side,100%patients haveThrombocytopeniacases,93.3%patients have microangiopathic hemolytic anemia,90%patients haveneurologic abnormalities,but fever (61.7%) and renal abnormalities (60%) are relatively rare.46casesof censorship in our group of patients with TTP ADAMTS13examination,41patients (89.1%)detected ADAMTS13deficiency,10.9%of patients with plasma ADAMTS13activity is normal,showing that the detection of plasma ADAMTS13activity has a good supporting value to diagnose ofTTP. In our study, TTP patients mortality rate is30%(9patients died in the hospital during treatment;another9patients give up treatment, left the hospital due to poor economic reasons or efficacy, outsidethe hospital were death). Statistical analysis of clinical laboratory indicators valid and death groupsfound,in the admission age of onset (95%confidence interval, p=0.0081) and high total bilirubin level(95%confidence interval, p=0.036) in patients plasmapheresis efficacy were less sensitive to poorprognosis. All of the TTP patients, those have13patients relapse, the relapse rate was21.7%, beforerelapse there had no obvious incentive(1patient was relapsed after cessation of therapy outside thehospital), To continue to observed the track of the treatment in relapse patients, there can effectivelyreduce relapse frequency used rituximab and second-line immune suppression based on the routine useof plasma exchange. In addition, the improved treatment of patients with plasma ADAMTS13inhibitordetection sustained positive should be noted that the recurrence of the disease.ConclusionTTP is a medical acute and severe disease, which have a higher rate of misdiagnosis rate. There haveno "gold standard" to diagnostic,its typical pentalogy exist rate is low (only30%), mainly diagnosis isbased on clinical manifestations with its typical blood count and blood chemistry changes, and except for other possible microvascular thrombotic disease. Therefore,when clinical have unexplainedthrombocytopenia, hemolytic anemia and other symptoms,we should be highly suspected TTP,and thenuse plasma exchange treatment to reduce mortality. Plasma exchange is still the preferred method oftreatment in TTP, at the same time, the higher the age at onset and total bilirubin level represent the poorprognosis, we should increase the Plasmapheresis amount and frequency, and in combination withrituximab and second-line immunosuppressive agents could reduce mortality and recurrence rate. Forthe patients with the high ADAMTS13antibody, we should detect the plasma ADAMTS13antibodyregularly, which could used to predict disease recurrence. Antithrombin(AT) is one of the most important anticoagulant substances in human body, it is arelative molecular weight of about58.2kD glycoprotein secreted by liver cells, belonging to the superfamily of serine protease inhibitor (SERPIN). Its anticoagulant is effected by inhibition of thrombin andactivated coagulation factor IX, X, XI and XII activity, in order to achieve the balance of coagulation inbody, and its role accounted is approximately70%of the total activity of the anticoagulant system.Long-term basic and clinical research has confirmed that AT deficiency is a genetic risk factor forthrombophilia, especially in the Asian population, it is easily leading to thrombosis formation whensome of the anticoagulant protein quantity or quality defects.Hereditary antithrombin deficiency is caused by mutations in the AT gene, its always have autosomaldominant inheritance laws with a family history. The proband usually have the deep vein thrombosis orpulmonary embolism that can not explain as the main performance. Our group have3probands thathave the main reason for treatmentcaught is deep vein thrombosis and mesenteric arterial thrombosis.The plasma level of AT antigen and AT activity were measured by enzyme-linked immunosorbent assayand chromogenic substrates in our laboratory. It was found that a family is type I AT deficiency; other2family are type II antithrombin deficiency. The part of the affected members in each family have thesame laboratory test results with the probands, but there have no clinical thromboembolic events thatconfirmed hereditary antithrombin deficiency thave significant individual differences in the clinical manifestations.All of the7exons and flanking sequence of antithrombin gene were amplified by PCR.The genesequence was analysed by direct sequencing. Three kinds of heterozygous mutation were found,there were2nonsense mutations and1missense mutation(T401X, R132X, L78P). T401Xand L78P were novel mutations. The part of the affected members in each family have thesame gene mutation with the probands. It is confirmed that three patients with hereditaryantithrombin deficiency caused by AT gene mutations, which indused to the antithrombindecreased in plasma, and lead to venous thromboembolism. The molecular characteristicsof AT mutation provide important information for the study of the relationship ofantithrombin structure and function.