Disorders of platelets

The study aimed to investigate hemostasis system of myeloma patients. Platelet , PT, APTT, TT, fibrinogen, Ethanol test, euglobulin lysis time, D- Dimer were mesured in 45 patients with myeloma. The result shows that patients with myeloma have disorders in the coagulant balance with hypocoagulability. There is a positive correlation between elevated blood protein negative correlation between elevated blood protein and PT% and APTT, TT; Tóm tắt Nhằm mục đích đánh giá hệ thống đông cầm máu ở bệnh nhân đa u tuỷ xương, chúng tôi tiến hành các XN…..

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Differential Diagnosis The differential diagnosis between DIC and severe liver disease is challenging and requires serial measurements of the laboratory parameters of DIC. Patients with severe liver disease are at risk for bleeding and manifest laboratory features including thrombocytopenia (due to platelet sequestration, portal hypertension, or hypersplenism), decreased synthesis of coagulation factors and natural anticoagulants, and elevated levels of FDP due to reduced hepatic clearance. However, in contrast to DIC, these laboratory parameters in liver disease do not change rapidly.

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Coagulation Disorders Associated with Liver Failure The liver is central to hemostasis because it is the site of synthesis and clearance of most procoagulant and natural anticoagulant proteins and of essential components of the fibrinolytic system. Liver failure is associated with a high risk of bleeding due to deficient synthesis of procoagulant factors and enhanced fibrinolysis. Thrombocytopenia is common in patients with liver disease and may be due to congestive splenomegaly (hypersplenism), or immune-mediated shortened platelet life span (primary biliary cirrhosis).

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The central mechanism of DIC is the uncontrolled generation of thrombin by exposure of the blood to pathologic levels of tissue factor (Fig. 110-3). Simultaneous suppression of physiologic anticoagulant mechanisms and abnormal fibrinolysis further accelerate the process. Together these abnormalities contribute to systemic fibrin deposition in small and mid-sized vessels. The duration and intensity of the fibrin deposition can compromise the blood supply of many organs, especially the lung, kidney, liver, and brain, with consequent organ failure.

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Metabolic and Inflammatory Disorders Acute febrile illnesses may result in vascular damage. This can result from immune complexes containing viral antigens or the viruses themselves. Certain pathogens, such as the rickettsiae causing Rocky Mountain spotted fever, replicate in endothelial cells and damage them. Vascular purpura may occur in patients with polyclonal gammopathies but more commonly in those with monoclonal gammopathies, including Waldenstrom's macroglobulinemia, multiple myeloma, and cryoglobulinemia.

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von Willebrand Disease vWD is the most common inherited bleeding disorder. Estimates from laboratory data suggest a prevalence of approximately 1%, but data based on symptomatic individuals suggest that it is closer to 0.1% of the population. vWF serves two roles: (1) as the major adhesion molecule that tethers the platelet to the exposed subendothelium; and (2) as the binding protein for FVIII, resulting in significant prolongation of the FVIII half-life in circulation.

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Patients with type 2 vWD have functional defects; thus, the vWF antigen measurement is significantly higher than the test of function. For types 2A, 2B, and 2M, vWF activity is decreased, measured as ristocetin cofactor or collagen binding activity. In type 2A vWD, the impaired function is due either to increased susceptibility to cleavage by ADAMTS13, resulting in loss of intermediate- and high-molecular weight (M.W.) multimers, or to decreased secretion of these multimers by the cell.

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Thrombotic Thrombocytopenic Purpura TTP and HUS were previously considered overlap syndromes. However, in the past few years the pathophysiology of inherited and idiopathic TTP has become better understood and clearly differs from HUS. TTP was first described in 1924 by Eli Moschcowitz and characterized by a pentad of findings that include microangiopathic hemolytic anemia, thrombocytopenia, renal failure, neurologic findings, and fever. The full-blown syndrome is less commonly seen now, probably due to earlier diagnosis.

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Hemolytic Uremic Syndrome HUS is a syndrome characterized by acute renal failure, microangiopathic hemolytic anemia, and thrombocytopenia. It is seen predominantly in children and in most cases is preceded by an episode of diarrhea, often hemorrhagic in nature. Escherichia coli O157:H7 is the most frequent, although not only, etiologic serotype. HUS not associated with diarrhea (termed DHUS) is more heterogeneous in presentation and course.

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Laboratory Testing for HIT HIT (antiheparin/PF4) antibodies can be detected using two types of assays. The most widely available is an enzyme-linked immunoassay (ELISA) with PF4/polyanion complex as the antigen. Since many patients develop antibodies but do not develop clinical HIT, the test has a low specificity for the diagnosis of HIT. This is especially true in patients who have undergone cardiopulmonary bypass surgery, where approximately 50% of patients develop these antibodies postoperatively.

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Immune Thrombocytopenic Purpura: Treatment The treatment of ITP utilizes drugs that decrease reticuloendothelial uptake of the antibody-bound platelet and/or decrease antibody production. However, the diagnosis of ITP does not necessarily mean that treatment must be instituted. Patients with platelet counts 30,000/µL appear not to have increased mortality related to the thrombocytopenia.

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Table 109-1 Drugs Definitively Reported to Cause Isolated Thrombocytopeniaa Abciximab Digoxin Acetaminophen Eptifibatide Acyclovir Hydrochlorothiazide Aminosalicylic acid Ibuprofen Amiodarone Levamisole Amphotericin B Octreotide Ampillicin Phenytoin Carbamazepine Quinine Chlorpropamide Rifampin Danazol Tamoxifen Diatrizoate meglumine (Hypaque Meglumine) Tirofiban Trimethoprim/sulfamethoxazole Diclofenac Vancomycin a Drugs that preceded thrombocytopenia and full recovery occurred after drug discontinuation, but recurred with re-introduction of the drug, and ot...

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Thrombocytopenia Thrombocytopenia results from one or more of three processes: (1) decreased bone marrow production; (2) sequestration, usually in an enlarged spleen; and/or (3) increased platelet destruction. Disorders of production may be either inherited or acquired. In evaluating a patient with thrombocytopenia, a key step is to review the peripheral blood smear and to first rule out "pseudothrombocytopenia," particularly in a patient without an apparent cause for the thrombocytopenia. Pseudothrombocytopenia (Fig.

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Approach to the Patient: Thrombocytopenia The history and physical examination, results of the CBC, and review of the peripheral blood smear are all critical components in the initial evaluation of the thrombocytopenic patients (Fig. 109-2). The overall health of the patient and whether he/she is receiving drug treatment will influence the differential diagnosis. A healthy young adult with thrombocytopenia will have a much more limited differential diagnosis than an ill hospitalized patient who is receiving multiple medications.

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Harrison's Internal Medicine Chapter 109. Disorders of Platelets and Vessel Wall Disorders of Platelets and Vessel Wall: Introduction Hemostasis is a dynamic process in which the platelet and the blood vessel wall play key roles. Platelets become activated upon adhesion to von Willebrand factor (vWF) and collagen in the exposed subendothelium after injury. Platelet activation is also mediated through shear forces imposed by blood flow itself, particularly in areas where the vessel wall is diseased, and is also affected by the inflammatory state of the endothelium.

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Anemia occurs in ~80% of myeloma patients. It is usually normocytic and normochromic and related both to the replacement of normal marrow by expanding tumor cells and to the inhibition of hematopoiesis by factors made by the tumor. In addition, mild hemolysis may contribute to the anemia. A larger than expected fraction of patients may have megaloblastic anemia due to either folate or vitamin B12 deficiency. Granulocytopenia and thrombocytopenia are very rare.

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Complications The major clinical complications of PV relate directly to the increase in blood viscosity associated with red cell mass elevation and indirectly to the increased turnover of red cells, leukocytes, and platelets with the attendant increase in uric acid and cytokine production. The latter appears to be responsible for the increase in peptic ulcer disease and for the pruritus associated with this disorder, although formal proof for this has not been obtained. A sudden massive increase in spleen size can be associated with splenic infarction or progressive cachexia.

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Hematologic Syndromes: Introduction The elevation of granulocyte, platelet, and eosinophil counts in most patients with myeloproliferative disorders is caused by the proliferation of the myeloid elements due to the underlying disease rather than a paraneoplastic syndrome. The paraneoplastic hematologic syndromes in patients with solid tumors are less well characterized than the endocrine syndromes because the ectopic hormone(s) or cytokines responsible have not been identified in most of these tumors (Table 96-2).

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Epistaxis is a common symptom, particularly in children and in dry climates, and may not reflect an underlying bleeding disorder. However, it is the most common symptom in hereditary hemorrhagic telangiectasia and in boys with vWD. Clues that epistaxis is a symptom of an underlying bleeding disorder include lack of seasonal variation and bleeding that requires medical evaluation or treatment, including cauterization. Bleeding with eruption of primary teeth is seen in children with more severe bleeding disorders, such as moderate and severe hemophilia.

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Systemic causes of nonpalpable purpura fall into several categories, and those secondary to clotting disturbances and vascular fragility will be discussed first. The former group includes thrombocytopenia (Chap. 109), abnormal platelet function as is seen in uremia, and clotting factor defects. The initial site of presentation for thrombocytopenia-induced petechiae is the distal lower extremity.

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