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Inherited bleeding disorders.

Congenital bleeding disorders comprise a heterogeneous group of diseases that reflect abnormalities of blood vessels, coagulation proteins and platelets. Studies of these diseases, many of which are rare and several of which result in a mild bleeding diathesis only, have significantly increased our understanding of normal haemostasis. Two lessons have been learned. First, quantitative abnormalities of coagulation proteins and platelets are an important, but not the only, cause of significant haemorrhage; some cases of inherited bleeding disorders reflect synthesis of a dysfunctional coagulation protein or production of abnormal platelets. Diagnostic tests that reflect qualitative abnormalities are therefore important in the evaluation of selected patients with inherited bleeding disorders. Second, in occasional patients the inherited disorder is complex and reflects combined abnormalities of coagulation proteins alone or in association with platelet disorders. In clinical practice it is useful to distinguish disorders that cause significant clinical bleeding from those that cause few or no symptoms. Examples of the former include severe deficiencies of factors VIII and IX, and the homozygous forms of factor II, V, VII, X, XI, XIII, fibrinogen and von Willebrand factor. Comparable platelet disorders include the inherited thrombocytopenias with platelet counts less than 20 x 10(9) litre-1 and the homozygous forms of Bernard-Soulier syndrome and Glanzmann's thrombasthenia. The most frequently encountered mild haemostatic abnormalities include type I von Willebrand's disease, the platelet storage pool deficiency syndromes and the mild and moderate forms of haemophilia A and B; occasionally heterozygous or homozygous forms of the rarer coagulation disorders, e.g. factor XI deficiency, may present with a mild bleeding diathesis. Finally, some disorders are entirely asymptomatic, e.g. factor XII deficiency and deficiencies of other contact coagulation factors. Management of patients with inherited bleeding disorders should reflect knowledge of the specific disorder to be treated plus careful consideration of the clinical circumstance for which therapy is proposed. In all cases, once a decision to treat has been made, the safest efficacious therapy should be given (for example DDAVP in the treatment of patients with mild haemophilia A or type I von Willebrand's disease). Although blood products are now much safer and the risk of blood transmitted viral infections is low, there still remains a risk that transfusion of any blood product may be associated with serious side-effects. As a result, therapy should be given only after careful consideration of the risk: benefit ratio and not merely to treat an abnormal laboratory result.(ABSTRACT TRUNCATED AT 400 WORDS)

Afibrinogenemia↗

[Genetic heterogeneity of ischemic (coronary) heart disease].

Results are presented on a study of the blood coagulation system and some indices of serum lipids and proteins in 133 normal individuals and probands with ischaemic heart disease and their 681 relatives. The examination of the relatives of probands with different types of biochemical disorders revealed a similar biochemical background in the probands and the members of their families. The disorders in blood biochemistry in the probands were most similar in the parents, the children of the probands' siblings, and less distinct in more distant relatives (cousins, nephews and nieces, etc.), biochemical disorders similar to those of the probands being found in young persons (14-16 years old) and reappearing in several generations. The author concludes on the genetic heterogeneity of ischaemic (coronary) heart disease and underlying coronary atherosclerosis.

Adult↗

The inhibitory effects of anticoagulation on in vivo gene transfer by adeno-associated viral or adenoviral vectors.

Identifying factors that influence gene transfer efficacy is critical for a successful gene-based clinical study. Here we demonstrate that in vivo AAV-2-mediated gene transfer is efficiently inhibited by unfractionated heparin, but not by a heparin preparation containing mainly low-molecular-weight forms (LMWH). Surprisingly, inhibitors of thrombin or factor Xa (F.Xa) significantly reduced AAV-2 transduction in a dose-dependent manner. These effects were independent of the vector promoter, transgene, or strain of mice. Expression by alternate AAV serotypes 5 and 8 was not affected by anticoagulant drugs, which suggests an AAV-2-specific effect. Moreover, AAV-2-mediated gene expression was diminished in mice with deficiency in thrombin generation (factor IX deficiency) and enhanced in mice with procoagulant phenotype due to factor V Leiden. In addition, inhibitors of F.Xa diminished adenovirus-mediated gene expression. These results demonstrated that coagulation activity itself is critical to ensure optimal viral vector transduction. Since intravascular delivery of vectors often requires the use of anticoagulants, the use of LMWH appears to be safe. These observations are of relevance for approaches using AAV-2 or adenoviral vectors, especially in early phase studies designed to identify the minimum therapeutic doses.

Adenoviridae↗

A multicenter clinical evaluation of the Clot Signature Analyzer.

BACKGROUND: The Clot Signature Analyzer (CSA) was designed to assess global hemostasis as a screening assay using non-anticoagulated whole blood. Three different measurements are produced by the instrument: platelet hemostasis time (PHT), clot time (CT), and collagen-induced thrombus formation (CITF). OBJECTIVES: The purpose of the present study was to determine normal ranges for these measurements and assess the performance of the CSA in patients with well-characterized hemostatic disorders and in normal subjects. PATIENTS AND METHODS: Four institutions participated in the study. Each established their own normal reference ranges. Patients with well-characterized hemostatic disorders and concurrent normal controls were subsequently examined. RESULTS: Normal ranges between institutions were similar although statistically different. One hundred and eight patients were examined: 46 individuals with von Willebrand disease (VWD) (type 1, 26; type 2A, 11; type 2B, six; type 3, three); 38 patients with a coagulation factor deficiency; 13 individuals with platelet function defects; 10 patients taking warfarin; and one individual on low-molecular-weight heparin. Of these patients, 89% had at least one abnormality by CSA: 42/46 VWD patients, 35/38 coagulation protein defect patients, 9/13 patients with platelet function defects, 9/10 patients on warfarin and 1/1 patient on low-molecular-weight heparin. Of 116 normal subjects, 103 (89%) fell within the centers' normal range. These data suggest that the CSA has a good sensitivity for bleeding disorders.

Adult↗

Genetic diagnosis of haemophilia and other inherited bleeding disorders.

Inherited deficiencies of plasma proteins involved in blood coagulation generally lead to lifelong bleeding disorders, whose severity is inversely proportional to the degree of factor deficiency. Haemophilia A and B, inherited as X-linked recessive traits, are the most common hereditary hemorrhagic disorders caused by a deficiency or dysfunction of blood coagulation factor VIII (FVIII) and factor IX (FIX). Together with von Willebrand's disease, a defect of primary haemostasis, these X-linked disorders include 95% to 97% of all the inherited deficiencies of coagulation factors. The remaining defects, generally transmitted as autosomal recessive traits, are rare with prevalence of the presumably homozygous forms in the general population of 1:500,000 for FVII deficiency and 1 in 2 million for prothrombin (FII) and factor XIII (FXIII) deficiency. Molecular characterization, carrier detection and prenatal diagnosis remain the key steps for the prevention of the birth of children affected by coagulation disorders in developing countries, where patients with these deficiencies rarely live beyond childhood and where management is still largely inadequate. These characterizations are possible by direct or indirect genetic analysis of genes involved in these diseases, and the choice of the strategy depends on the effective available budget and facilities to achieve a large benefit. In countries with more advanced molecular facilities and higher budget resources, the most appropriate choice in general is a direct strategy for mutation detection. However, in countries with limited facilities and low budget resources, carrier detection and prenatal diagnosis are usually performed by linkage analysis with genetic markers. This article reviews the genetic diagnosis of haemophilia, genetics and inhibitor development, genetics of von Willebrand's disease and of rare bleeding disorders.

Blood Coagulation Disorders, Inherited↗

Further investigations on antithrombin III in the plasmas of patients with the abnormality of antithrombin III Budapest.

Antithrombin III (AT-III) was studied in a thrombophilic family with an abnormal AT-III molecule (antithrombin III Budapest) using a modified crossed immunoelectrophoresis technique, gel filtration, 'rocket' immunoelectrophoresis and a heparin cofactor assay. When agarose was applied in the first phase of the crossed immunoelectrophoresis, the normal and the pathological AT-III revealed identical electrophoretic mobility. However, when heparin was mixed with agarose in the first phase of electrophoresis, the propositus' plasma displayed a different AT-III pattern from normal plasma. His plasma contained the first component of the normal plasma (Immune Antithrombin III1, IAT-III) in a concentration of only 5% of normal, and a protein in high concentration which although immunoreactive to AT-III antisera, had an electrophoretic mobility similar (but not identical to that of IAT-III2. This abnormal protein had no heparin cofactor activity and a molecular size greater than normal plasma AT-III. Unlike AT-III, the addition of heparin did not change the molecular size of the pathogic AT-III molecule significantly. The abnormal protein was present in lower concentrations in the patient's children and at the time of study they had no clinical or laboratory evidence of intravascular coagulation.

Adult↗

Protein Z levels in haemodialysis patients.

Protein Z (PZ) is a vitamin K-dependent protein isolated from human and bovine plasmas. Although the exact role of PZ in the haemostatic system is presently unknown, it is suggested that PZ deficiency may cause bleeding tendency. Haemostatic alterations in end-stage renal failure (ESRF) are certainly complex and involve several abnormalities in the coagulation and fibrinolytic system. In order to elucidate the detail of the haemostasis in ESRF, we aimed to investigate PZ activity in haemodialysis patients. Therefore, we compared plasma PZ levels in 10 haemodialysis patients (6 M, 4 F, mean age 36+/-11) and 10 healthy normal controls (5 M, 5 F, mean age 34+/-8) in this study. We found mean plasma PZ levels in haemodialysis patients and healthy controls 6.95+/-2.93 microg/ml and 3.06+/-0.81 microg/ml, respectively (p<0.005). Increased level of PZ which influences the action of thrombin on its protein substrates and inhibitors may contribute to the haemostatis alterations in ESRF patients, in addition to other well known abnormalities in the coagulation and fibrinolytic system.

Adult↗

Effects of human mast cell tryptase and eosinophil granule proteins on the kinetics of blood clotting.

Hypereosinophilic syndromes are often associated with thrombosis through unclear mechanisms, and mastocytosis has been associated with a variety of bleeding disorders. The present studies were aimed at defining the roles and interactions of eosinophil and mast cell constituents on the kinetics of blood clotting as measured by thromboelastograms. Eosinophil granule proteins and purified eosinophil peroxidase markedly reduced the anticoagulant properties of the mast cell tryptase/heparin complex. Moreover, eosinophil peroxidase by itself functioned as a powerful procoagulant and also inhibited the anticoagulant actions of heparin in a chromogenic assay for antithrombin III/factor Xa activity. The anticoagulant activity of the tryptase/heparin complex was attributable exclusively to the associated heparin and not to the intrinsic enzymatic activity of tryptase. Eosinophil granule proteins also strongly inhibited the enzymatic activity of tryptase in the presence of hydrogen peroxide, thus implicating a critical role for eosinophil peroxidase. We conclude that eosinophil granule proteins and eosinophil peroxidase both function as powerful procoagulants and also inhibit the anticoagulant and enzymatic activities of mast cell tryptase. The present results thus provide a mechanistic rationale for the well-established link between certain eosinophilic inflammatory disorders and hypercoagulant states. They also suggest that eosinophils may play an important role in neutralizing the anticoagulant activity of mast cell tryptase/heparin in various diseases.

Antithrombin III↗

Activation of the contact-phase system on bacterial surfaces--a clue to serious complications in infectious diseases.

Fever, hypotension and bleeding disorders are common symptoms of sepsis and septic shock. The activation of the contact-phase system is thought to contribute to the development of these severe disease states by triggering proinflammatory and procoagulatory cascades; however, the underlying molecular mechanisms are obscure. Here we report that the components of the contact-phase system are assembled on the surface of Escherichia coli and Salmonella through their specific interactions with fibrous bacterial surface proteins, curli and fimbriae. As a consequence, the proinflammatory pathway is activated through the release of bradykinin, a potent inducer of fever, pain and hypotension. Absorption of contact-phase proteins and fibrinogen by bacterial surface proteins depletes relevant coagulation factors and causes a hypocoagulatory state. Thus, the complex interplay of microbe surface proteins and host contact-phase factors may contribute to the symptoms of sepsis and septic shock.

Animals↗

Elevated total plasma homocysteine, a risk factor for thrombosis. Relation to coagulation and fibrinolytic parameters.

Homocystinuria is a rare inherited metabolic disease. Arterial and venous thromboembolic events represent frequent and life-threatening complications in homocystinuric patients. It has been suggested that mild homocysteinemia could be a risk factor for vascular disease. We have therefore measured total plasma homocysteine (HCy) concentrations by radioisotopic assay in 50 subjects with venous or arterial thrombosis and studied the relationship between HCy, coagulation and fibrinolytic parameters. Values were considered abnormal if they were higher than 2.7 standard deviations (SD) above the mean, i.e., 14.1 mmol/l. Thus, eighteen of the 50 patients with thrombosis were classified in the hyperhomocysteinemia group. Nine of these subjects had only this isolated risk factor. No correlations were found between HCy and antithrombin III, protein C, protein S and plasminogen levels, or plasma plasminogen activator inhibitor activity. Nevertheless, the correlation between tissue-plasminogen activator antigen and total plasma HCy was significant (r = 0.61, p < 0.001). Increased homocysteinemia seems to be a risk factor for thrombotic events especially knowing that HCy presents a direct cytotoxic effect. Vitamin therapy, already used in homozygote homocystinuric patients, might be beneficial in the prevention of thromboembolic disease in heterozygous patients.

Adolescent↗

Coagulopathy with the use of hetastarch in the treatment of vasospasm.

The use of colloid agents to achieve hypervolemia in the prevention and treatment of postsubarachnoid hemorrhage (post-SAH) vasospasm is included in the standard of care at many institutions. Risk profiles are necessary to ensure appropriate use of these agents. In a series of 85 patients with recent aneurysmal SAH, 26 developed clinical symptoms of vasospasm. Fourteen of the 26 were treated with hetastarch for volume expansion while the other 12 received plasma protein fraction (PPF). Clinically significant bleeding pathologies were noted in six patients who received hetastarch as a continuous intravenous infusion. Hetastarch increased partial thromboplastin time from a mean of 23.9 seconds to a mean of 33.1 seconds (p < 0.001) in all patients who received infusions of this agent, while no effect was noted in the 12 patients who received PPF infusions. No other coagulation parameters were altered. This study shows an increase in coagulopathy with the use of hetastarch as compared with the use of PPF for the treatment of postaneurysmal vasospasm.

Blood Coagulation Disorders↗