Age-Dependent Changes in the Incidence and Etiology of Childhood Thrombocytosis

Abstract

To determine the incidence and etiology of childhood thrombocytosis, over 15,000 platelet counts in 7,539 patients performed at a single regional hospital were reviewed. When thrombocytosis was defined as ≧500 × 10⁹/l of platelet counts, the condition could be diagnosed in 6.0% (456 cases) of the patients. All patients were classified as having secondary thrombocytosis. The incidence of thrombocytosis dramatically changed throughout child development; it was 12.5% in neonates, peaked to 35.8% in 1-month-old infants and then returned to 12.9% in 6- to 11-month-old infants. Thereafter, it gradually decreased with age to only 0.6% in 11- to 15-year-old children. Frequent causes of thrombocytosis included infection (67.5%), Kawasaki disease (9.4%), prematurity (7.7%) and iron deficiency anemia (6.4%). Thrombocytosis was an incidental finding in a substantial population of early infants. Thrombocytosis as a reaction to several types of infection and Kawasaki disease was more common in children under 7 years old, while autoimmune disease and tissue damage were major causes in children aged 11–15 years. No child had thromboembolic complications. These findings indicate that childhood thrombocytosis is a benign condition and its incidence and etiology seem to depend on age.

Primary thrombocytosis in children

“…Most of these children had thrombocytosis that could be characterized as mild, but others transiently reached levels over 900,000. [17][18][19][20] Causes of secondary thrombocytosis are many and varied (Table 1). Infection is the most common, including viral and bacterial pathogens, and both acute and chronic infections.…”

Thrombocytosis in neonates and young infants: a report of 25 patients with platelet counts of ⩾1 000 000 μl−1

“…17 The term 'reactive' is used to imply that platelet production has increased as a reaction to an underlying condition, generally an infectious or inflammatory disorder. [2][3][4][5][6][7]9,20 Thromboembolic and hemorrhagic complications are rare in patients with reactive thrombocytosis and anti-platelet or cytoreductive treatments are not usually needed, unless other risks are identified. 20,21 Thrombocytosis can also be classified according to severity, as judged by the peak platelet count.…”

“…Postoperative reactive thrombocytosis is also well known, with peak platelet counts at 7 to 20 days after surgery. [2][3][4][5][6][7]9,10,28 We found extreme thrombocytosis at a median of 13 days postoperatively. In adults, postoperative thrombocytosis is sometimes considered a risk factor for thrombotic complications, 10 but no vaso-occlusive or hemorrhagic events were detected in our patients.…”

“…Thrombocytosis has been reported in patients with hemolytic anemia or iron deficiency. [2][3][4][5][6][7]12,20,21,27,30,31 None of our four anemic patients had recognized hemolysis and all were thought to have the anemia of prematurity. Although elevated platelet counts have been observed in anemic patients receiving human recombinant erythropoietin, 32 none in our current study had received this medication.…”

“…1 Thrombocytosis has been reported in neonates and young infants, in which it has variably been defined as a platelet count of >400 000, >600 000 or >900 000 ml À1 . [2][3][4][5][6][7] We recently reported platelet counts of over 47 000 of the subjects obtained during the first 90 days after birth, and observed that the 95th percentile upper reference range can be as high as 750 000 ml À1 . 8 Adult patients with very high platelet counts can be at risk for significant thromboembolic and/or hemorrhagic complications, [9][10][11][12][13][14][15][16][17][18][19][20] but it is unclear whether similar risks exist for young infants.…”