Analysis of Clinical Characteristics and Risk Factors for Severe Disease in Mycoplasma pneumoniae Pneumonia Among Children Under 5 Years of Age

Background: In recent years, there has been an increasing trend of Mycoplasma pneumoniae (MP) infection at younger ages. To investigate the clinical characteristics of Mycoplasma pneumoniae pneumonia (MPP) in children under 5 years of age and to identify independent risk factors for severe MPP, aiming to provide a basis for early identification and intervention. A retrospective study was conducted among hospitalized children under 5 years of age diagnosed with MPP at Shanghai Children’s Hospital from January to December 2023. The patients were categorized into severe and non-severe groups based on disease severity. Clinical features, laboratory findings, and imaging data were compared between the two groups. Least absolute shrinkage and selection operator (LASSO) regression and multivariate logistic regression analysis was used to identify independent risk factors and construct a predictive model. The predictive performance of the model was assessed using the receiver operating characteristic (ROC) curve. A total of 494 children with MPP were included, comprising 238 (48.2%) in the severe group and 256 (51.8%) in the non-severe group. Compared with the non-severe group, the severe group exhibited higher peak body temperature, longer pre-admission duration of fever, longer fever duration, more severe chest radiographic manifestations, and longer hospital length of stay (all P<0.05). The severe group also demonstrated a significantly higher incidence of lethargy, tachypnea, pulmonary moist rales, and liver injury, in addition to a higher rate of bronchoalveolar lavage (BAL) procedures (all P<0.05). Four independent predictors were identified through LASSO regression and multivariate logistic regression: chest radiographic scores（OR=3.879,95%CI:2.623-5.736）, fever duration（OR=1.149, 95%CI:1.058-1.248）, wheeezing（OR=2.516, 95%CI:1.405-4.505, and l ethargy （OR=3.135, 95%CI:1.022-9.617）, The constructed nomogram model achieved area under the curve (AUC) values of 0.814 (95% CI: 0.769–0.859) in the training set and 0.765 (95% CI: 0.688–0.842) in the validation set, respectively. Conclusion: Chest radiographic scores, fever duration, wheezing and lethargy constitute key risk factors for progression to severe MPP in children under 5 years of age. The nomogram model developed in this study demonstrates good discriminatory performance and may serve as an objective basis for early identification of high-risk patients and implementation of stratified management.