thrombocytopenia

n. decrease in the number of platelets in the blood

Thrombocytopenia (or -paenia, or thrombopenia in short) is the presence of relatively few platelets in blood.Generally speaking a normal platelet count ranges from 150,000 and 450,000 per mm3. These limits, however, are determined by the 2.5th lower and upper percentile, and a deviation does not necessarily imply any form of disease. The number of platelets in a blood sample also decreases rather quickly with time and a low platelet count may be caused by a delay between sampling and analysis.
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Thrombocytopenia is an abnormal drop in the number of blood cells involved in forming blood clots. [more]Thrombocytopenia - Community and Resources

Noun
1. a blood disease characterized by an abnormally small number of platelets in the blood
(synonym) thrombopenia
(hypernym) blood disease, blood disorder
(hyponym) essential thrombocytopenia

A decrease in the number of platelets in the blood that may result in easy bruising and excessive bleeding from wounds or bleeding in mucous membranes and other tissues.