目的 了解儿童继发性血小板增多症的临床特点，帮助临床医师提升诊治水平。方法 回顾性分析2021年1月至12月收治的继发性血小板增多症患儿的临床资料，总结其发病原因，年龄、性别分布，炎症因子特点。结果 纳入386例继发性血小板增多症患儿，平均发病年龄（2.0±0.3）岁，<3岁患儿294例（76.2%）。中位血小板计数为626.5（567.8~701.0）×10⁹/L，在病程8.0（7.0~11.0）天，血小板计数达到高峰，然后逐渐下降。143例患儿在病程恢复期规律监测血常规，血小板在病程10.0（7.0~14.0）天恢复正常。引起继发性血小板增多症最常见的原因为感染（94.6%），感染最常见的3种病原体为肺炎支原体、真菌和腺病毒。继发性血小板增多症患儿的白细胞介素（IL）-1β、IL-2受体、IL-6、IL-8、IL-10及肿瘤坏死因子（TNF）-α水平均高于血小板正常的患儿，差异有统计学意义（P<0.05）。结论 继发性血小板增多症多见于3岁以下儿童，最常见的原因是感染。针对原发病治疗后血小板即可恢复正常，除川崎病，其余患儿均无需抑制血小板聚集及抗凝治疗。

Objective To understand the clinical characteristics of secondary thrombocythemia in children, and to help clinicians improve their diagnosis and treatment. Methods The clinical data of children with secondary thrombocythemia admitted from January to December 2021 were retrospectively analyzed to summarize the causes of the disease, age and gender distribution, and characteristics of inflammatory factors. Results Three hundred and eighty-six children with secondary thrombocythemia were included, with a mean age of onset of (2.0±0.3) years, and 294 children (76.2%) were<3 years old. The median platelet count was 626.5 (567.8-701.0)×10⁹/L, which peaked at 8.0 (7.0-11.0) days of the disease course and then gradually declined.143 children were regularly monitored for blood counts during the recovery period, and platelets returned to normal at 10.0 (7.0-14.0) days of the disease course. The most common cause of secondary thrombocythemia was infection (94.6%), and the three most common pathogens of infection were Mycoplasma pneumoniae, fungi, and adenovirus. The levels of interleukin (IL)-1β, IL-2 receptor, IL-6, IL-8, IL-10, and tumor necrosis factor (TNF)-α were higher in children with secondary thrombocythemia than in those with normal platelets, and the difference was statistically significant (P<0.05). Conclusion The secondary thrombocythemia is most common in children under 3 years of age, and the most common cause is infection. Platelets can be normalized after treatment for the primary disease, and no inhibition of platelet aggregation and anticoagulation is needed in all children except Kawasaki disease.