Mycoplasma pneumoniae pneumonia (MPP) is community-acquired pneumonia (CAP) occurring commonly in children in our country. The clinical features and treatment outcomes of MMP are thought to be closely associated with age and radiographic progression. However, studies have investigated the age-specific combined with radiographic features in patients with MPP are scarce.

We aimed to investigate the clinical manifestations in children with MPP at different ages and to determine the risk factors for lobar pneumonia so as to provide reference for its precise treatment.

This was a retrospective study. The clinical data of 895 children with MPP who were hospitalized at Department of Pediatrics, Hunan Provincial People's Hospital/The First Affiliated Hospital of Hunan Normal University between August 2023 and April 2024 were included in the study and divided into the group with aged <5 years old and the group with aged≥5 years old according to age. Different age groups were further divided into subgroups (lobar pneumonia and non-lobar pneumonia) according to the chest imaging findings. The clinical data, laboratory findings, treatments and outcomes were collected and analyzed. To use the method based on Taqman fluorescent probe RT-PCR for detecting MP-DNA and drug resistant gene. Multivariate Logistic regression models were used to identify the risk factors for lobar pneumonia.

Of the 895 patients with MPP we studied, 418 of whom (46.7%) were male, 477 of whom (53.3%) were female. The median age of the children was 7.1 years (interquartile range, 5.1 to 8.9). The clinical data of 218 (24.4%) patients with MPP aged <5 years old and further divided into the study subgroup with 164 (18.3%) cases (non-lobar pneumonia) and 54 (6.0%) cases (lobar pneumonia). The clinical data of 677 (75.6%) patients with MPP aged≥5 years old, and further divided into the study subgroup with 304 (34.0%) cases (non-lobar pneumonia) and 373 (41.7%) cases (lobar pneumonia). The proportion of female patients, age, cough, fever, decreased breath sounds, headache, dizziness, proportion of peak temperature≥39.0 ℃, proportion of sore throat, fever duration, neutrophil percentage, neutrophil-to-lymphocyte ratio (NLR), C-reactive protein, platelet-to-lymphocyte ratio (PLR), D-dimer level, proportion of mycoplasma pneumoniae (MP) resistance, proportion of bronchoalveolar lavage, proportion of methylprednisolone treatment, proportion of lobar pneumonia and length of hospital stay were higher in the≥5-year-old group than in the <5-year-old group. In contrast, the proportions of wheezing, rales, three-concave sign, white blood cell count (WBC), albumin, lactate dehydrogenase (LDH), glutamic transaminase level, intravenous immunoglobulin usage, non-invasive continuous positive airway pressure (CPAP) ventilation, proportion of nasal cannula oxygen therapy, and pediatric intensive care unit (PICU) admission were lower in the≥5-year-old group (all P<0.05). The median age, proportion of allergic constitution, proportion of heat peak ≥39.0 ℃, proportion of pulmonary respiratory sound attenuation, WBC and MP resistance, proportion of bronchoscopy, proportion of methylprednisolone treatment, and length of hospital stay in the <5-year-old non lobar pneumonia subgroup were higher than those in the <5-year-old non lobar pneumonia subgroup (P<0.05). In the≥5-year-old lobar pneumonia subgroup, the proportions of allergic constitution, fever peak≥39 ℃, proportion of decreased breath sounds, D-dimer, drug resistance, bronchoscopy, methylprednisolone, and length of hospital stay were higher than those in the≥5-year-old non-lobar pneumonia subgroup, while the proportions of wheezing, three-concave sign, and oxygen therapy were lower than those in the≥5-year-old non-lobar pneumonia subgroup, with statistically significant differences (P<0.05). Multivariate Logistic stepwise regression analysis showed that age≥5 years, allergic constitution, fever peak≥39.0 ℃, elevated NLR, and MP drug resistance were risk factors for lobar pneumonia (P<0.05).

The pulmonary signs in the <5-year-old age group are more obvious, requiring more oxygen therapy and PICU support; while the extrapulmonary symptoms in the≥5-year-old group are more prominent, with a longer hospital stay, prone to progression to lobar pneumonia, a high incidence of drug resistance, and more common needs for glucocorticoids and bronchoalveolar lavage treatment. Age≥5 years, allergic constitution, fever peak≥39.0 ℃, elevated NLR, and drug resistance are risk factors for the occurrence of lobar pneumonia.