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The Increased Percentage of Megathrombocytes in Various Clinical Disorders

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Supported by a grant from the New York Heart Association, New York, N.Y., and by grant HE13336-02 from the National Institutes of Health, Bethesda, Md.

▸Requests for reprints should be addressed to Simon Karpatkin, M.D., Department of Medicine, New York University Medical School, 550 First Ave., New York, N.Y., 10016.

New York, New York

Ann Intern Med. 1972;77(3):361-367. doi:10.7326/0003-4819-77-3-361
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Large platelets, or megathrombocytes, have been shown to be young platelets recently released from the marrow. The percentage of megathrombocytes was measured in patients with clinical disorders and normal platelet counts where increased platelet turnover might be suspected. Increased megathrombocytes were noted in 68% of 41 patients with systemic lupus erythematosus; 47% of 14 patients with chronic autoimmune thrombocytopenic purpura in apparent remission; 52% of 10 patients with disseminated intravascular coagulation; 14% of 22 surgical patients, 2 hours after surgery; 48% of 19 patients with rheumatic heart disease and severe valvular impairment; 20% of 25 patients with prosthetic heart valves and rheumatic heart disease; and 30% of 15 patients with diabetes mellitus and retinopathy. We observed that [1] clinical "remission" in patients with chronic autoimmune thrombocytopenic purpura may be more apparent than real; [2] the diagnosis of disseminated intravascular coagulation can be suspected if there is a normal platelet count but an increase in the percentage of megathrombocytes; [3] there was less evidence for increased platelet turnover in patients with prosthetic heart valves and rheumatic heart disease than in patients with rheumatic heart disease and severe valvular involvement.





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