Correlation and predictive value of TLR2, MyD88, and MUC5AC in bronchial mucus plug formation in children with mycoplasma pneumoniae pneumonia: a prospective study

Background Bronchial mucus plugs (BMPs) are a severe complication of Mycoplasma pneumoniae pneumonia (MPP) in children. This study aimed to investigate the potential mechanisms underlying BMP formation based on biomarkers in bronchoalveolar lavage fluid (BALF) and to develop a predictive model for clinical risk assessment of BMP formation. Methods This prospective study enrolled 151 children with MPP hospitalized at the First Affiliated Hospital of Xinxiang Medical University between July 2023 and February 2025. According to the presence of BMPs, patients were classified into BMP ( n = 66) and non-BMP ( n = 85) groups. BALF levels of Toll-like receptor 2 (TLR2), myeloid differentiation primary response 88 (MyD88), and mucin 5AC (MUC5AC) were determined via ELISA. Key risk factors identified through LASSO and support vector machine (SVM) were used to construct a multivariate logistic regression-based nomogram, and evaluate its predictive performance. Spearman correlation and serial mediation analyses were employed to explore the TLR2/MyD88/MUC5AC axis in BMP formation. Results Compared with the non-mucus plug group, children in the mucus plug group exhibited significantly higher BALF levels of TLR2, MyD88, and MUC5AC (all P < 0.001). D-dimer, TLR2, and MUC5AC were identified as independent risk factors for BMP formation. The nomogram demonstrated favorable predictive performance (AUC = 0.914, 95%CI: 0.871–0.958) with good calibration and clinical utility. Significant positive correlations were observed among TLR2, MyD88, and MUC5AC. After adjustment for potential confounders, Serial mediation analysis suggested that the association between TLR2 and bronchial mucus plug formation may involve a serial pathway mediated by MyD88 and MUC5AC.(standardized effect β = 0.026, 95%CI: 0.007–0.052). Conclusion In children with MPP, TLR2 may be associated with BMP formation, and this association may partially involve a serial pathway including MyD88 and MUC5AC. D-dimer, TLR2, and MUC5AC are independent risk factors for this condition. The derived nomogram demonstrates high discriminative power and accuracy and may serve as a risk stratification tool during bronchoscopic evaluation to identify children at high risk of extensive mucus plugging and support individualized airway management.