title: 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 > or =500 x 10(9)/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.
authors.affiliation: Department of Pediatrics, Nishi-Kobe Medical Center, Kobe, Japan. kskmatsu@portnet.ne.jp
authors.forename: Kousaku
authors.initials: K
authors.lastname: Matsubara
authors.forename: Takashi
authors.initials: T
authors.lastname: Fukaya
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nigami
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Harigaya
authors.forename: Takuya
authors.initials: T
authors.lastname: Hirata
authors.forename: Hideo
authors.initials: H
authors.lastname: Nozaki
authors.forename: Kunizo
authors.initials: K
authors.lastname: Baba
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D000367:Age Factors; D018798:Anemia, Iron-Deficiency / Q000150:complications; D001327:Autoimmune Diseases / Q000150:complications; D002648:Child; D002675:Child, Preschool; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature; D007239:Infections / Q000150:complications; D009080:Mucocutaneous Lymph Node Syndrome / Q000150:complications; D010976:Platelet Count; D013922:Thrombocytosis / Q000453:epidemiology* / Q000209:etiology