ABSTRACT
Thrombocytosis is a frequent finding in hemograms obtained from hospitalized and ambulatory children due to the widespread use of automated blood cell counters. Pediatricians are commonly puzzled in cases of thrombocytosis to determine the underlying cause and the need for therapy. The purpose of this review is to assist the general pediatrician into dealing with this common hematological finding in every day clinical practice. Fortunately, primary thrombocytosis or essential thrombocythemia, a clonal disease, is exceedingly rare in childhood, but may be associated with thromboembolic and hemorrhagic complications. On the other hand, secondary or reactive thrombocytosis is very common and is due to a variety of conditions, such as acute and chronic infections, iron deficiency, bleeding, hemolytic anemias, collagen vascular diseases, malignancies, drugs and splenectomy. Treatment of reactive thrombocytosis should be directed to the underlying problem alone. Administration of platelet aggregation inhibitors such as aspirin is unwarranted. Consultation is necessary only for the rare child with extreme thrombocytosis who has clinical and/or laboratory criteria consistent with essential thrombocythemia, or in whom a hemorrhagic or thrombotic complication has developed.