Independent Risk Factors and Combined Predictive Model for Severe Mycoplasma pneumoniae Pneumonia in Children: The Role of Vitamin D Deficiency

Objectives: Vitamin D deficiency had been associated with the pathophysiology of respiratory infections. This research sought to assess the correlation between disease severity, serum 25-hydroxyvitamin D [25(OH)D] and lung function in children with Mycoplasma pneumoniae pneumonia (MPP). Methods: A cohort of 102 children with MPP aged 6–17 years was recruited. All enrolled participants were 6–14 years old, and they were categorised into a mild group (n = 50) and a severe group (n = 52). Between-group comparisons were performed for demographic characteristics, serum 25(OH)D concentrations, laboratory indicators, imaging results, and pulmonary function. Logistic regression was employed to determine risk variables, and their predictive ability for SMPP was examined by ROC. Results: The severe group had markedly reduced serum 25(OH)D concentrations compared to the mild group (17.23 ± 6.81 vs. 20.49 ± 6.09 ng/mL; p = 0.013). Fever duration was prolonged, and CRP, LDH, D-dimer, NLR, AST and IL-6 were elevated in the severe group (all p < 0.05). Moreover, pleural effusion and pulmonary consolidation were more commonly observed in the severe group (p < 0.05). Pulmonary function showed no disparities between groups. Logistic regression identified 25(OH)D < 12 ng/mL (OR = 11.31), elevated CRP (OR = 1.033), elevated LDH (OR = 1.009), prolonged fever duration (OR = 1.552), and pleural effusion (OR = 41.86) as independent risk variables for SMPP. The integrated model produced an AUC of 0.866 (95% CI: 0.795–0.937), demonstrating 88.5% sensitivity and 74.0% specificity. Conclusions: 25(OH)D < 12 ng/mL, elevated CRP and LDH, prolonged fever duration, and pleural effusion are associated with severe pneumonia in children with MPP aged 6–14 years. Their combined use has exploratory predictive potential for identifying severe disease in children with MPP.