Objective: To analyze the clinical features of children with infection-related eosinophilic lung diseases (ELD) caused by common respiratory pathogens.

Methods: A retrospective cohort study was conducted. The clinical features, auxiliary examinations, treatments, and prognoses of 134 children with infection-related ELD caused by common respiratory pathogens at Yuying Children's Hospital from January 2014 to June 2024 were collected. Participants were divided into the mild and severe groups based on whether the proportion of eosinophils in bronchoalveolar lavage fluid (BALF) exceeded 0.25. Chi-square test or Fisher's exact test was used to analyze the differences between the two groups, and Logistic regression was performed to examine the correlation between BALF eosinophilia and the clinical outcomes.

Results: Among the 134 children, 73 were males and 61 were females, with an age of 6.9 (4.6, 8.8) years on admission. A total of 154 pathogen detections were recorded, including 116 cases (75.3%) of Mycoplasma pneumoniae, 8 cases (5.2%) of influenza A virus, 6 cases (3.9%) of Streptococcus pneumoniae, and 6 cases (3.9%) of Chlamydia pneumoniae, among others. The percentage of eosinophils in the BALF of all children was 0.10 (0.07, 0.15). There were 117 cases in the mild group and 17 cases in the severe group. Compared with the mild group, significantly greater proportion of children in the severe group presented dyspnea (10/17 vs. 17.1% (20/117)), wheezing (7/17 vs. 8.5% (10/117)), respiratory failure (8/17 vs. 7.7% (9/117)), single lobe ≥2/3 consolidation (7/17 vs. 12.8% (15/117)), atelectasis (7/17 vs. 12.0% (14/117)), pleural effusion (7/17 vs. 16.2% (19/117)), plastic bronchiolitis (4/17 vs. 4.3% (5/117)), and systemic corticosteroid prescription (14/17 vs. 51.3% (60/117)) (all P<0.05). Univariate Logistic regression analysis revealed that severe eosinophilia in BALF was significantly associated with an elevated risk of respiratory failure (OR=10.67, 95%CI 3.31-34.38, P<0.001), single lobe ≥2/3 consolidation (OR=4.76, 95%CI 1.57-14.41, P=0.006), atelectasis (OR=5.15, 95%CI 1.69-15.72, P=0.004), pleural effusion (OR=3.61, 95%CI 1.22-10.67, P=0.020), and plastic bronchitis (OR=6.89, 95%CI 1.64-28.94, P=0.008). Among the 126 children who were followed up, 106 cases (84.1%) were cured, 20 cases (15.9%) improved, and no relapses or deaths occurred.

Conclusions: Mycoplasma pneumoniae and influenza A virus are common pathogens in children with infection-related ELD and the percentage of eosinophils in BALF is mildly increased, and the severe cases exhibit more severe clinical features and more significant pulmonary abnormalities, such as lobar consolidation and lung atelectasis. The prognosis is generally favorable.