Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0012739 (disseminated intravascular coagulation)
 8,673 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

After clinical assessment, pertinent history, and family history, the clinician often has a good idea concerning the cause of a patient's bleeding. The most appropriate laboratory tests can then be ordered. Routine screening tests include a complete blood cell count, platelet count, and evaluation of a peripheral blood sample, a prothrombin time, and an activated partial thromboplastin time. Thrombocytopenia may result from idiopathic thrombocytopenic purpura, disseminated intravascular coagulation, or, less commonly, acute leukemia, aplastic anemia, thrombotic thrombocytopenic purpura, or a particular drug that a patient is taking. Again, the patient's history, physical findings, and evaluation of a well-prepared peripheral blood smear will be helpful in determining the cause of the patient's thrombocytopenia. An isolated prolongation of the activated partial thromboplastin time may result from low levels of factors VIII, IX, or XI. A slightly prolonged activated partial thromboplastin time and a moderate decrease in factor VIII may reflect von Willebrand disease or the "carrier" state for hemophilia A. In women a greatly prolonged activated partial thromboplastin time and very low levels of factor VIII (< 3%) most often result from an acquired factor VIII inhibitor (autoantibody against factor VIII) or from severe (type III) von Willebrand disease. If von Willebrand disease is suspected (because of menorrhagia with or without other mucous membrane bleeding, a positive family history, and a prolonged activated partial thromboplastin time), more specific laboratory tests for this disease should be done. These include assays of factor VIII, von Willebrand factor antigen, von Willebrand factor activity (measured by the ristocetin cofactor assay), and template bleeding time. In von Willebrand disease the defect is in von Willebrand factor. The affected individual may have subnormal levels of structurally and functionally normal von Willebrand factor (this is called "classic" or type I von Willebrand disease) or may produce von Willebrand factor that is structurally and functionally abnormal (von Willebrand disease type 2). Individuals who inherit a gene for von Willebrand disease from both parents have severe (type 3) von Willebrand disease and will have extremely low levels (< 3%) of von Willebrand factor and factor VIII and will have a very prolonged bleeding time. In most populations type I disease is the most common form, whereas type 3 is the least commonly encountered form. It should be noted that levels of von Willebrand factor can be influenced by the patient's blood type (persons who have blood type AB have 60% to 70% higher levels than do persons who have blood type O) and can be elevated during pregnancy, stress, and hyperthyroidism. The two major functions of von Willebrand factor are to serve as a "bridge" between platelets and injury sites in blood vessel walls and to protect circulating factor VIII from rapid proteolytic degradation. Thus, if a patient has either too little or functionally abnormal von Willebrand factor, the bleeding time will be prolonged and factor VIII will be decreased (because it is not being protected by von Willebrand factor). It should be determined which type of von Willebrand disease a particular patient has because treatment depends on type. Multimeric analysis of von Willebrand factor can be done with use of sodium dodecyl sulfate gels, radiolabeled antibody to von Willebrand's factor, and autoradiography. This will allow visualization of the multimeric structure of von Willebrand factor. In type I disease all bands are present, whereas in the type 2 variants 2A and 2B no high-molecular-weight multimers are seen. Desmopressin acetate (which is available in parenteral form for intravenous use and in a highly concentrated intranasal spray formulation) is the treatment of choice for classic type I disease. The drug effects a rapid release of von Willebrand factor from endothelial cell stor
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PMID:Screening and diagnosis of coagulation disorders. 882 61

Elevated plasma concentrations of von Willebrand factor (vWf) are increasingly recognized as a cardiovascular risk factor, and are used as a marker of endothelial activation. However, the factors which determine the rate of vWf release from the endothelium in vivo have not been defined clearly. In addition, vWf plasma levels may also be influenced by adhesion of vWf to the vascular wall or to platelets, and by its rate of degradation. The propeptide of vWf (also called vWf:AgII) is stored and released in equimolar amounts with vWf. In the present study we attempted to determine whether this propeptide could be a more reliable marker of endothelial secretion than vWf itself. To accomplish this we developed an ELISA based on monoclonal antibodies. The propeptide levels in normal plasma were found to be 0.7 microgram/ml, more than 10 times lower than vWf itself. Administration of desmopressin (DDAVP) induced a rapid relative increase in propeptide (from 106 to 879%) and in vWf (from 112 to 272%). However, the increases in vWf and propeptide were equivalent when expressed in molar units. A time course study indicated a half-life of the propeptide of 3 h or less. In a baboon model of disseminated intravascular coagulation (DIC) induced by FXa, vWf increased by less than 100%, whereas the propeptide concentrations increased by up to 450%. In view of the massive thrombin generation (as assessed by fibrinogen depletion), the increases in vWf are small, compared to the strong secretory response to thrombin and fibrin previously observed in vitro. Our results suggest that due to its rapid turnover, the propeptide could provide a sensitive plasma marker of acute endothelial secretion.
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PMID:Acute von Willebrand factor secretion from the endothelium in vivo: assessment through plasma propeptide (vWf:AgII) Levels. 915 1

Appropriate laboratory testing for the platelet-type bleeding disorders hinges on an adequate assessment in the history and physical examination. Patients with histories and screening laboratory results consistent with coagulation disorders (hemophilia, disseminated intravascular coagulation) are not appropriate candidates for platelet function testing. In contrast, patients with a lifelong history of platelet-type bleeding symptoms and perhaps a positive family history of bleeding would be appropriate for testing. Figure 6 depicts one strategy to evaluate these patients. Platelet morphology can easily be evaluated to screen for two uncommon qualitative platelet disorders: Bernard-Soulier syndrome (associated with giant platelets) and gray platelet syndrome, a subtype of storage pool disorder in which platelet granulation is morphologically abnormal by light microscopy. If the bleeding disorder occurred later in life (no bleeding with surgery or trauma early in life), the focus should be on acquired disorders of platelet function. For those patients thought to have an inherited disorder, testing for vWD should be done initially because approximately 1% of the population has vWD. The complete vWD panel (factor VIII coagulant activity, vWf antigen, ristocetin cofactor activity) should be performed because many patients will have abnormalities of only one particular panel component. Patients diagnosed with vWD should be classified using multimeric analysis to identify the type 1 vWD patients likely to respond to DDAVP. If vWD studies are normal, platelet aggregation testing should be performed, ensuring that no antiplatelet medications have been ingested at least 1 week before testing. If platelet aggregation tests are normal and if suspicion for an inherited disorder remains high, vWD testing should be repeated. The evaluation of thrombocytopenia may require bone marrow examination to exclude primary hematologic disorders. If future studies with thrombopoietin assays confirm preliminary results, however, the bone marrow examination of certain patients may be replaced by a thrombopoietin level.
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PMID:Overview of platelet physiology and laboratory evaluation of platelet function. 1037 Aug 53