Immune dysregulation and pathogen prevalence in Mycoplasma pneumoniae pneumonia: a retrospective insight in children.

OBJECTIVE: To explore the etiological characteristics and lymphocyte subtype features of pediatric mycoplasma pneumonia complicated with pleural effusion, clarify the influencing factors and predictive indicators of its occurrence, and analyze the manifestations of immune dysregulation in the children. METHODS: This study retrospectively selected 104 children diagnosed with mycoplasma pneumonia in the pediatric department of our hospital from February 2023 to February 2025. The age range was 1-13 years old. They were divided into the mycoplasma pneumonia with pleural effusion group (46 cases) and the non-pleural effusion group (58 cases) based on chest ultrasound examination. Pathogenic identification was performed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry, and qRT-PCR. Peripheral blood lymphocyte subsets (CD3⁺T, CD4⁺T, CD8⁺T, CD19⁺B, CD56⁺NK) were analyzed by flow cytometry. Risk factors were identified using multivariate logistic regression, and their predictive performance was evaluated using receiver operating characteristic (ROC) curve analysis. RESULTS: Among the 104 children with Mycoplasma pneumoniae, the incidence of pleural effusion was 44.23% (46/104). A total of 59 pathogens were detected in the respiratory specimens of the aforementioned children. Among them, viruses accounted for the highest proportion (44.07%), followed by Mycoplasma pneumoniae (32.20%) and bacteria (23.73%). Mixed infections accounted for 66.10%, while single infections accounted for 33.90%. Compared with the non-effusion group, the levels of CD3 + T, CD4 + T, and CD8 + T were reduced in the complicated group, while the levels of CD19 +B and CD56 +NK were significantly increased (P < 0.05). α1-AG, CRP, and GAG were independent risk factors for pleural effusion, with OR values of 2.277 (95% CI: 1.365-3.800), 1.982 (95% CI: 1.245-3.155), and 2.502 (95% CI: 1.480-4.229), respectively (P < 0.05). The combined detection of α1-AG, CRP, and GAG achieved an AUC of 0.924, with sensitivity of 89.13% and specificity of 87.93%, significantly outperforming any single marker. CONCLUSION: Among the 104 children diagnosed with mycoplasma pneumonia, viral pathogens were the most frequently detected in the respiratory tract, and the proportion of mixed infections was relatively high. Children with pleural effusion showed more significant immune dysfunction. The combined prediction model of these three indicators has a high diagnostic value (AUC = 0.924), providing a reference for early clinical warning.