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A condition characterized by an increase in the absolute number of thrombocytes in the circulation. Also known as piastrenemia; thrombocythemia.



an increase in the number of platelets to more than 400,000 per mm3 in the peripheral blood. It may result from the increased production of platelets in the bone marrow, as in erythremia; from slow lysis of platelets, for example, after surgical removal of the spleen; or from the redistribution of platelets in the bloodstream during physical or mental stress. Thrombocytosis may lead to thrombosis, and occasionally to an increased tendency to bleed owing to disturbance of the microcirculation or to defects in the platelets themselves (thrombocytolytic purpura). Therapy involves treatment of the underlying disease, as well as the prevention of thrombosis.

References in periodicals archive ?
We hope that further studies performed on larger number of patients--reactive thrombocytosis- and controls, additionally including thrombo-cythemic disorders, with the possibility of encountering higher platelet counts and analyzing additional criteria that could influence viscosity can illuminate the dark spots of current clinical practice in reactive thrombocytosis which seems innocent at the present.
Postsplenectomy reactive thrombocytosis. Proc (Bayl Univ Med Cent) 2009; 22 (1): 9-12
Reactive thrombocytosis and stroke following cardiopulmonary bypass surgery: Case report on three patients.
Hang and Teu (19) found that 78% cases of reactive thrombocytosis may be due to infections.
700-900 x [10.sup.9]/L has been found in approximately 6-8% of children with reactive thrombocytosis and only 0.5-3% have platelet count > 1000 x [10.sup.9]/L.1920 Fouzas S et al (21) studied 408 infants and found 25.2% had SBI.
Evidence of an increased in vitro thrombotic tendency in patients with reactive thrombocytosis is of paramount importance in proving the cause and effect relationship between reactive thrombocytosis and thromboembolism.
After obtaining Royal Perth Hospital Ethics Committee approval (EC2009/098), a total of 48 patients with reactive thrombocytosis, defined by platelet count >500 x [10.sup.9]/l, and 55 randomly selected patients who did not have thrombocytosis in the intensive care unit (ICU) were recruited.
The relationship between reactive thrombocytosis and evidence of having a strong in vitro thrombotic tendency (MA >80 mm) was analysed by multivariable logistic regression after adjusting for clinical and laboratory variables that were associated with a P value <0.25 in the univariable analyses.
A total of 54 patients with reactive thrombocytosis were recruited during the study period between July 2010 and June 2011.
Patients with reactive thrombocytosis were significantly more likely to demonstrate evidence of an increased in vitro thrombotic tendency than were patients in the control group without evidence of reactive thrombocytosis (MA >74 mm: 77 vs 29%, P=0.001, and mean MA 77 vs 69 mm, mean difference 8 mm, 95% confidence interval 4.9 to 10.9, P=0.001, respectively) (Table 2).
Reactive thrombocytosis is the most common type of thrombocytosis.
(4) Nonstandard abbreviations: RT, reactive thrombocytosis; MPD, myeloproliferative diseases; ET, essential thrombocythemia; PV, polycythemia vera; CML, chronic myeloid leukemia; PLT, platelet count; MPV, mean platelet volume; PDW, platelet distribution width; and MF, myelofibrosis.

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