Mycoplasma pneumoniae pneumonia with and without viral pathogens in preschool-aged children: a comparative study of clinical outcomes.

BACKGROUND

Viral co-infections are common in pediatric Mycoplasma pneumoniae pneumonia (MPP), yet their age-specific clinical impact on children under six is not fully understood. We aimed to describe the frequency, pathogen-specific inflammatory signatures, and age-dependent clinical impact of viral co-detection in this population.

METHODS

In this retrospective study, we collected data from the medical records of 504 children hospitalized with MPP between July 2021 and December 2024. The information extracted included clinical manifestations, laboratory findings, treatment modalities, and the presence of viral co-infections.

RESULTS

Viral co-detection occurred in 193 (38.3%) children, peaking in the 2-4 years age group (47.1%). Among children under 2 years, co-detection was associated with a higher severe disease rate (29.7% vs. 9.5%; P = 0.046). Compared to rhinovirus (HRV) co-detection, human metapneumovirus (HMPV) and respiratory syncytial virus (RSV) co-detections were linked to more pronounced inflammatory responses. HMPV co-detection was characterized by leukopenia [median: 2.25 (IQR 1.73-3.05) vs. 2.70 (1.72-7.31) × 10⁹/L, P = 0.013] and elevated IL-10 [8.76 (5.58-18.66) vs. 5.00 (2.97-5.95) pg/mL, P = 0.037] and IFN-γ [4.34 (2.68-5.96) vs. 2.24 (1.12-2.77) pg/mL, P = 0.028]. RSV co-detection featured a neutrophilic response, with higher neutrophil counts [5.76 (4.11-7.36) vs. 3.93 (2.69-4.06) × 10⁹/L, P = 0.033], neutrophil-to-lymphocyte ratio [2.87 (1.57-4.30) vs. 1.17 (0.62-2.13), P = 0.003], and IL-10 levels [10.97 (7.74-20.23) vs. 5.00 (2.97-5.95) pg/mL, P = 0.024]. Multivariable analysis identified wheezing (aOR=1.909; 95% CI: 1.131-3.222), severe pneumonia (aOR=1.797; 95% CI:1.019-3.169), and higher serum IL-10 (aOR=1.038 per unit; 95% CI: 1.015-1.062) as independent risk factors associated with viral co-detection. In contrast, children aged 4-6 years had a significantly lower risk of co-detection compared to those under 2 years (aOR=0.528; 95% CI: 0.308-0.903) (all P < 0.05).

CONCLUSION

Viral co-detection in preschool children with MPP is associated with more severe clinical outcomes, particularly in those under two years of age. Our findings identify pathogen-specific immune response patterns (driven by HMPV and RSV) and elevated serum IL-10 as key risk markers. These findings are hypothesis-generating; the observed associations do not establish causality, and require validation in prospective studies before informing clinical practice.