目的 分析儿童原发性免疫性血小板减少症（primary immune thrombocytopenia, pITP）与以血小板减少为首发表现的结缔组织病患儿初诊时的临床与免疫特征，为早期鉴别提供依据。 方法 回顾性选取2019年1月—2024年8月收治的216例pITP（pITP组）和20例以血小板减少为首发表现的结缔组织病相关血小板减少症（connective tissue disease-related thrombocytopenia, CTD-TP）（CTD-TP组）患儿为研究对象，比较两组临床、免疫指标差异，分析早期鉴别的可能影响因素及效能。 结果 CTD-TP组发病年龄较大，白细胞计数、嗜酸性粒细胞、淋巴细胞计数和补体C4均低于pITP组（P<0.05）；C-反应蛋白、IgE和IgM高于pITP组（P<0.05）；logistic回归分析显示，年龄、IgE、IgM、总B细胞和补体C4是早期鉴别pITP与CTD-TP的预测因素（P<0.05）；受试者操作特征曲线分析显示5项指标联合具有较好的鉴别效能（曲线下面积为0.944）。相关性分析显示pITP组IgG与血小板计数呈负相关（r_s =-0.363，P<0.05）；CTD-TP组NK细胞与血小板计数呈正相关（r_s =0.713，P<0.05）。 结论 pITP与CTD-TP患儿初诊临床及免疫学指标存在异质性，研究结果有助于两种疾病的早期鉴别。

Objective To investigate the clinical and immunological features of children with primary immune thrombocytopenia (pITP) or connective tissue disease (CTD) with thrombocytopenia as the initial manifestation at initial diagnosis, and to provide a basis for early differentiation. Methods A retrospective study was performed on 236 children with pITP (pITP group) or CTD with thrombocytopenia as the initial manifestation (CTD-TP group) who were admitted from January 2019 to August 2024. Clinical and immunological indicators were compared between the two groups to identify potential influencing factors for early differentiation and their discriminative validity. Results Compared with the pITP group, the CTD-TP group had a significantly older age of onset and significantly lower leukocyte count, eosinophil count, lymphocyte count, and complement C4 level (P<0.05), as well as significantly higher levels of C-reactive protein, IgE, and IgM (P<0.05). The logistic regression analysis showed that age, IgE, IgM, total B cells, and complement C4 were predictive factors for early differentiation between pITP and CTD-TP (P<0.05). The receiver operating characteristic curve analysis showed that a combination of these five factors had a good discriminative validity, with an area under the curve of 0.944. The correlation analysis showed a negative correlation between IgG and platelet count in the pITP group (r_s =-0.363, P<0.05) and a positive correlation between NK cells and platelet count in the CTD-TP group (r_s =0.713, P<0.05). Conclusions There is heterogeneity in the clinical and immunological indicators between children with pITP and CTD-TP at initial diagnosis, and these research findings can help with the early differentiation between the two diseases.