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PubMed2002

Thrombocytosis: too much of a good thing?

Thrombocytosis is due to (a) a variety of disorders that cause reactive stimulation of platelet production, (b) familial mutations, or (c) essential thrombocythemia (ET) and other myeloproliferative disorders (MPDs). The MPDs are clonal abnormalities of the pluripotent hematopoietic stem cell. Dysregulation of megakaryocytopoiesis in ET involves defective binding of thrombopoietin by platelets and megakaryocytes resulting in increased levels of plasma free thrombopoietin, and increased sensitivity of megakaryocytes to thrombopoietin leading to their increased proliferation. Bleeding and thrombosis are the major causes of morbidity and mortality in ET and the other MPDs. The elevated platelet count and qualitative platelet defects have been implicated in the pathophysiology of these hemostatic problems. However, these platelet abnormalities do not correlate well with clinical complications. It is proposed that bleeding and thrombosis could be due to vascular abnormalities that result from dysfunctional hematopoietic stem cell-derived endothelial cells.

Blood Platelets↗
PubMed1998

Cerebral vascular accidents in young patients with essential thrombocythemia: relation with other known cardiovascular risk factors.

BACKGROUND AND PURPOSE: Since the advent of routine automated blood cell counts, an increased platelet count often is detected fortuitously in asymptomatic individuals. In the past, essential thrombocythemia (ET) was thought to be linked to an increase incidence of hemorrhagic complications, whereas thrombosis is now considered more frequently. Actually, the risk of thrombosis cannot be predicted in an asymptomatic patient with essential thrombocythemia. PATIENTS AND METHODS: A total of 41 young patients (age range, 18 to 45 years) affected by ET and diagnosed in agreement with the Polycythemia Vera Study Group criteria are reported. Common risk factors, such as hypertension, smoke, obesity, dyslipidemia, and diabetes, have been registered. Particular attention has been given to cerebral vascular accidents (CVA) both of the arterial and venous systems. Platelet number, platelet serotonin content, and platelet aggregation under collagen, adenosine diphosphate (ADP), and adrenalin stimuli were evaluated. RESULTS: Nine out of the 41 patients affected by ET had CVAs, four of which occurred in the venous system. No difference in platelet function tests has been observed between patients with or without CVA. Six out of the 9 patients with ET and CVA had at least one atherosclerotic risk factor: four were heavy smokers, one had hypertension, and one had hypertension and obesity. CONCLUSIONS: Cerebral vascular accidents are confirmed to be frequent in patients with essential thrombocythemia, even at a young age. However, the presence of at least one atherosclerotic risk factor associated with increased platelet number seems to favor thrombotic complications. In particular, cigarette smoking seems to be related to arterial CVAs in essential thrombocythemia.

Adult↗
PubMed1990

Thrombocytosis in young people: evaluation of 57 cases diagnosed before the age of 40.

Over the past 13 years 57 cases of primary thrombocytosis in young people have been studied. Only patients with a platelet count over 500 x 10(9)/liter and a follow-up longer than 2 years were considered. Thrombocytosis in young people represents approximately 25% of total cases referred to our department during this period. The most common causes are essential thrombocythemia (20 cases) and secondary thrombocytosis (22 cases). The highest platelet counts are found in essential thrombocythemia patients. Most of our patients were discovered by a fortuitous hematological examination. In contrast, 5 out of the polycythemic patients were recognized after a thrombosis. The same was true for 2 out of 20 essential thrombocythemia subjects. Four subjects (2 essential thrombocythemia and 2 secondary thrombocytosis) were diagnosed after hemorrhages. The overall survival was very good except for leukemic patients and thrombocytosis secondary to neoplasms. Vascular complications after diagnosis were scarce: 2 polycythemia vera patients showed bleedings during antiaggregating therapy. None of our patients developed epithelial cancer, malignant lymphoma or myelofibrosis. Vascular traumata seem more frequent in polycythemia vera regardless of age. Therefore, it seems useful to treat polycythemic patients, while no therapy seems to be indicated in other forms of thrombocytosis.

Adult↗
PubMed1982

Profile of blood coagulation and fibrinolysis in chronic myeloproliferative disorders.

Blood coagulation and fibrinolysis were studied in 65 patients with chronic myeloproliferative disorders (MPD). They consisted of 28 patients with chronic granulocytic leukemia (CGL) in chronic phase, 7 with CGL in blast crisis, 9 with polycythemia vera (PV), 13 with primary thrombocythemia (PTh) and 8 with primary myelofibrosis (MF). Hemorrhagic and thrombotic complications were observed in 19 and 8 patients, respectively. Activated partial thromboplastin time and prothrombin time were prolonged in many patients. Low factor II levels were observed in some CGL patients. Factor V was decreased in CGL patients in chronic phase and in PV patients. Fibrinogen was either normal or increased in most patients, but an elevation of fibrin/fibrinogen degradation products (FDP) was found in some patients. The VIIIR: Ag/VIII:C ratio was increased in CGL patients in blast crisis, in PV patients and in PTh patients. Antithrombin III and plasminogen were below normal in some patients. Most patients showed a decrease in alpha 2-plasmin inhibitor. These findings suggest that blood coagulation and fibrinolysis are involved in the pathogenesis of the thrombotic and hemorrhagic complications in these patients. Chronic low-grade intravascular coagulation might be present in some patients with MPD.

Adult↗
PubMed1993

[Hemorrhage of upper digestive and respiratory tracts in children. A clinical, biological and therapeutic approach].

Haemorrhages in the upper aero-digestive tract, whether spontaneous or provoked by surgery, lead to the discovery of abnormal coagulation. A retrospective series of 43 children hospitalized for haemorrhage of the upper aero-digestive tract enabled us to evaluate the most frequent causes. Willebrand's disease, haemophilia and Glanzmann's thromboasthenia, primary haemostasis disease, made up 27.9% of the cases; acquired impaired haemostasis by thrombopathies secondary to aspirin intake accounted for 25.6%; finally the haemostasis tests were normal in 46.5% of the children. Based on clinical features and biological data, we proposed an adapted diagnostic approach and discussed therapy in light of the current literature. This study confirmed the importance of an adapted routine battery of laboratory tests and the persistent search for impaired haemostasis in children hospitalized for haemorrhage of the upper aero-digestive tract.

Adolescent↗
PubMed2000

Isolated spleen agenesis: a rare cause of thrombocytosis mimicking essential thrombocythemia.

Thrombocytosis is a common feature of myeloproliferative disorders but may also result from various conditions including chronic iron deficiency, hemorrhage, chronic inflammation and splenectomy. We report two cases of secondary thrombocytosis caused by isolated and congenital asplenia, mimicking essential thrombocythemia. These two adult cases of spleen agenesis were unexpected. We conclude that in thrombocytosis without clinical evidence of splenomegaly, attentive screening of blood in search of Howell-Jolly bodies and abdominal ultrasonography should always be performed not only to detect mild spleen enlargement but also to make sure of the presence of this organ.

Diagnosis, Differential↗
PubMed2001

Thrombocytosis and thrombocythemia.

Thrombocytosis is caused by three major pathophysiological mechanisms: (1) reactive or secondary thrombocytosis; (2) familial thrombocytosis; and (3) clonal thrombocytosis, including essential thrombocythemia and related myeloproliferative disorders. Recent work has begun to elucidate the abnormal megakaryocytopoiesis of essential thrombocythemia, which is associated with paradoxically elevated plasma levels of thrombopoietin. The clonal nature of all cases of essential thrombocythemia has been challenged. Thrombotic complications are the major causes of morbidity and mortality in this disease. Indications for platelet cytoreduction and antiplatelet therapy, as well as complications of treatment, are being clarified.

Clone Cells↗
PubMed1999

Clinicopathological diagnosis and differential criteria of thrombocythemias in various myeloproliferative disorders by histopathology, histochemistry and immunostaining from bone marrow biopsies.

Differentiation of essential thrombocythemia (ET) from thrombocythemias occurring in various subtypes of chronic myeloproliferative disorders (MPDs) is controversial, because of the lack of uniform clinical and morphological criteria. A retrospective clinicopathologic study was performed on 375 patients presenting with a MPD and a platelet count exceeding 500 x 10(9/)l. For comparison 35 patients with reactive thrombocytosis (RT) and five patients with a myelodysplastic syndrome (MDS-5q(-) syndrome) were enrolled into this study. In addition to a complete clinicopathological work-up, procedures included histochemical and immunological staining techniques and morphometry of bone marrow biopsies for proper evaluation of megakaryocytes (CD61) and erythroid precursors (Ret40f). Because of the high patient's age on admission, relative survival rates with corresponding disease-specific loss of life expectancy were calculated. Analysis of clinical and morphological characteristics, in particular megakaryopoiesis revealed features which enabled a clear-cut distinction between thrombocythemias in MPDs and thrombocythemic states in MDS. This rationale proved to be most important for the diagnostic discrimination of the 33 patients with initial (prefibrotic) stages of idiopathic myelofibrosis (IMF) from ET (40 patients). A new set of relevant criteria for the diagnosis of IMF with special regard to early stages and its distinction from ET has been proposed. Hemorrhagic episodes were more frequently observed in ET than in thrombocythemias associated with polycythemia vera (PV). Computation of specific loss of life expectancy revealed two extremes: thrombocythemia in CML (81%) and ET (3%), whereas thrombocythemias in PV and IMF did not show a significantly different life loss (19-22%). The revised criteria for ET, PV and IMF are reliable by taking histopathological features from bone marrow biopsies into consideration, particularly for the diagnosis of ET and its differentiation from thrombocythemias as a presenting symptom accompanying the various subtypes of MPDs.

Aged↗
PubMed1978

Platelet hyperaggregability and thrombosis in patients with thrombocythemia.

The relation between platelet hyperaggregability and thrombosis was assessed in 28 patients with thrombocythemia due to myeloproliferative diseases and 11 with reactive thrombocytosis. None of the patients with reactive thrombocytosis had thrombotic or hemorrhagic complications, but thrombosis was noted in seven patients and bleeding in two patients with thrombocythemia. Nineteen were asymptomatic. In patients with thrombosis, bleeding time, platelet glass retention, and clot retraction were normal, but evidence of platelet hyperaggregability was present in all but one. Serial studies on six patients revealed a close association between platelet hyperaggregability and ischemic attacks. Neither patient with bleeding complications had evidence of platelet hyperaggregability, although poor platelet function was found in one. Platelet function in asymptomatic patients can be classified as hyperactive, hypoactive, or normal.

Adult↗
PubMed2002

[Treatment of essential thrombocythemia with anagrelide: a ten-year experience].

Essential thrombocythemia (ET) is a chronic myeloproliferative syndrome characterized by thrombocythemia and increased megakaryocytes in bone marrow, thrombosis and/or hemorrhagic manifestations. We report here a ten-year experience in the treatment of ET with anagrelide (A), a non mutagenic drug that inhibits megakaryocyte maturation. Between April 1991 and June 2001, 54 ET patients were included with platelet counts > 900 x 10(9)/l in asymptomatic cases and > 600 x 10(9)/l in symptomatic ones. Age at diagnosis was 39 years (11-83). Previously 30 patients had received treatment with hydroxyurea, alpha INF, busulfan and/or 32P. At diagnosis 18 patients had microvascular obstruction, 7 thrombosis, 8 hemorrhagic manifestations and 3 both hemorrhage and thrombosis. Platelet counts at diagnosis were 1200 x 10(9)/l (600-3472) and before A 995 x 10(9)/l (520-2206). The follow-up from diagnosis was 68 months (9-172) and with A treatment 34 months (2-100). The A dose during the first week of treatment was 2.5 mg/d (1-3) and at maintenance 1.5 mg/d (1-3). Complete response was obtained in 96.3% cases, 77% with platelet counts < 400 x 10(9)/l, and 18.5% < 600 x 10(9)/l. The median time to obtain a complete response was 14 days. Transient adverse effects were present in 66% of patients (headache, nausea, abdominal distention, palpitation and edema). Mild to moderate anemia developed within 2-8 months in 40% of patients. During treatment 8 patients had microvascular obstruction with platelet counts over 400 x 10(9)/l and 7 with normal values. One patient developed myelofibrosis. Five patients died for reasons unrelated to ET. In conclusion, anagrelide was effective in reducing platelet counts and preventing mayor thrombotic events.

Adolescent↗
PubMed1993

[Secondary and primary thrombocythemia].

Reactive thrombocytosis is an elevation of platelet count occurring in association with certain underlying diseases such as various infections, inflammatory, neoplastic and asplenic states. Essential thrombocythemia is a myeloproliferative syndrome affecting megakaryocytes, which leads to increased numbers of circulating platelets. This disorder is characterized by splenomegaly and a clinical course punctuated by hemorrhagic and/or thrombotic episodes.

Diagnosis, Differential↗
PubMed1997

[Essential thrombocythemia in pregnancy. A case report and general considerations].

Essential thrombocythemia is a rare disease of unknown etiology characterized by an abnormal increase in the platelet count which cannot be explained by other identifiable causes such as malignancy, infection, chronic inflammatory diseases or other myeloproliferative disorders. It rarely affects people less than 50 years of age and may be associated with hemorrhagic or thrombotic tendencies. A care of pregnancy complicated by essential thrombocythemia treated with aspirin, antiaggregating agent, throughout pregnancy and with hydroxyurea, a platelet lowering drug is reported. Also examine are some pathogenetic and therapeutic aspects of the thrombotic tendency secondary to elevated platelet count in pregnancy.

Adult↗