[ Abstract ] Purpose This retrospective study aimed to identify risk factors for severe Mycoplasma pneumoniae pneumonia (SMPP) and plastic bronchitis (PB) in children, and to evaluate the predictive value of relevant biomarkers through receiver operating characteristic (ROC) curve analysis. Methods A total of 145 children with SMPP who underwent fiberoptic bronchoscopy at Dongguan People’s Hospital from April 2023 to April 2024 were enrolled, including 40 PB cases. A control group of 50 children with mild MPP was included. Clinical data, laboratory parameters were analyzed. Results 1.The univariate analysis revealed that age ≥6 years, fever duration ≥7 days, oxygen saturation <95%, and elevated IL-6 levels were significant risk factors for SMPP (P<0.05). 2. Multivariate logistic regression confirmed age >6 years and elevated serum IL-6 levels as independent risk factors for SMPP. 3. Compared to the SMPP group, the SMPP+PB group showed significantly higher rates of lung consolidation >50% on radiographs (P<0.05), longer fever duration (P<0.05), increased need for glucocorticoid/immunoglobulin therapy (P<0.05), and more frequent bronchoscopic interventions (P<0.05). However, no significant difference was observed in long-term outcomes (P>0.05). 4. The SMPP+PB group exhibited significantly higher serum IL-6, TNF-α, IFN-γ, and D-dimer levels compared to the SMPP group (P<0.05), whereas comparable MP genomic copy numbers were found in bronchoalveolar lavage fluid (BALF) (P>0.05). 5 The ROC analysis demonstrated that IL-6 had strong discriminatory power for disease severity (AUC=0.1),TNF-α, IFN-γ, and D-dimer effectively predicted PB (AUC=0.849, AUC=0.853, AUC=0.872, respectively). Conclusion Serum IL-6, TNF-α, IFN-γ, and D-dimer levels correlate with disease severity in pediatric MP infections, reflecting their roles in lung injury pathophysiology.