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.

Sutor AH: Thrombocytosis in childhood. Semin Thromb Hemost 1995;21:330–339.
Addiego JE Jr, Mentzer WC Jr, Dallman PR: Thrombocytosis in infants and children. J Pediatr 1974;85:805–807.
Chan KW, Kaikov Y, Wadsworth LD: Thrombocytosis in childhood: A survey of 94 patients. Pediatrics 1989;84:1064–1067.
Heath HW, Pearson HA: Thrombocytosis in pediatric outpatients. J Pediatr 1989;114:805–807.
Felici L, Freddara R, Pierani P, Coppa GV, Giorgi PL: Thrombocytosis in hospitalized children. J Pediatr 1990;116:835.
Vora AJ, Lilleyman JS: Secondary thrombocytosis. Arch Dis Child 1993;68:88–90.
Yohannan MD, Higgy KE, Al-Mashhadani SA, Santhosh-Kumar CR: Thrombocytosis. Etiologic analysis of 663 patients. Clin Pediatr 1993;33:340–343.
Wolach B, Morag H, Drucker M, Sadan N: Thrombocytosis after pneumonia with empyema and other bacterial infections in childhood. Pediatr Infect Dis J 1990;9:718–721.
Kilpi T, Anttila M, Kallio MJT, Peltola H: Thrombocytosis and thrombocytopenia in childhood bacterial meningitis. Pediatr Infect Dis J 1992;11:456–460.
Garoufi A, Voutsioti K, Tsapra H, Karpathios T, Zeis PM: Reactive thrombocytosis in children with upper urinary tract infection. Acta Paediatr 2001;90:448–449.
Ishiguro A, Nakahata T, Matsubara K, Hayashi Y, Kato T, Suzuki Y, Shimbo T: Age-related changes of thrombopoietin in children: Reference interval for serum thrombopoietin levels. Br J Haematol 1999;106:884–888.
Shulman ST, Inocencio JD, Hirsch R: Kawasaki disease. Pediatr Clin North Am 1995;45:1205–1222.
Buss DH, Cashell AW, O’Connor ML, Richards II F, Case LD: Occurrence, etiology, and clinical significance of extreme thrombocytosis: A study of 280 cases. Am J Med 1994;96:247–253.
Griesshammer M, Bangerter M, Sauer T, Wennauer R, Bergmann L, Heimpel H: Aetiology and clinical significance of thrombocytosis: Analysis of 732 patients with an elevated platelet count. J Intern Med 1999;245:295–300.
Nathan DG, Oski FA: Appendix iii; in: Nathan DG, Oski FA (eds): Hematology of Infancy and Childhood. Philadelphia, Saunders, 1993.
Kaushansky K: Thrombopoietin. N Engl J Med 1998;339:746–754.
Ishiguro A, Suzuki Y, Matsubara K, Kato T, Miyazaki Y, Shimbo T: Elevation of serum thrombopoietin precedes thrombocytosis in acute infection. Br J Haematol 2002;116:612–618.
Ishiguro A, Ishikawa T, Shimbo K, Matsubara K, Baba K, Hayashi Y, Naritaka S, Nakahata T: Elevation of serum thrombopoietin precedes thrombocytosis in Kawasaki disease. Thromb Haemost 1998;79:1096–1100.
Cerutti A, Custodi P, Duranti M, Cazzola M, Balduini CL: Circulating thrombopoietin in reactive conditions behaves like an acute phase reactant. Clin Lab Haematol 1999;21:271–275.
Matsubara K, Baba K, Nigami H, Harigaya H, Ishiguro A, Kato T, Miyazaki H: Early elevation of serum thrombopoietin levels and subsequent thrombocytosis in healthy preterm infants. Br J Haematol 2001;115:963–968.
Kapsoritakis AN, Potamianos SP, Sfiridaki AI, Koukourakis MI, Koutroubakis IE, Roussomoustakaki MI, Manousos ON, Kouroumalis EA: Elevated thrombopoietin serum levels in patients with inflammatory bowel disease. Am J Gastroenterol 2000;95:3478–3481.
Belman AL, Roque CT, Ancona R, Anand AK, Davis RP: Cerebral venous thrombosis in a child with iron deficiency and thrombocytosis. Stroke 1990;21:488–493.
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