Analysis of cytokine levels, cytological findings, and MP‐DNA level in bronchoalveolar lavage fluid of children with Mycoplasma pneumoniae pneumonia

BACKGROUND: The present study was conducted to determine the inflammatory response in the lungs of children with Mycoplasma pneumoniae pneumonia (MPP). METHODS: This study retrospectively analyzed cytokine levels, cytological findings, and M. pneumoniae (MP)‐DNA level in the bronchoalveolar lavage fluid (BALF) of 96 children with MPP. The study utilized Spearman's correlation method to evaluate the contribution of BALF and blood parameters in MPP children. RESULTS: (1) A total of 96 MPP children were classified into the Low MP‐DNA MPP group (BALF MP‐DNA ≤ 10(5) copies/mL) and the High MP‐DNA MPP group (BALF MP‐DNA > 10(5)copies/mL); the Non‐fever MPP group (no fever during the entire course of pneumonia) and the Fever MPP group; the Defervescence MPP group (fever had subsided at the time of bronchoscopy) and the Fervescence MPP group; and the Mild MPP group and the Severe MPP group. (2) The High MP‐DNA MPP, Fever MPP, Fervescence MPP, and Severe MPP groups had higher levels of interleukin (IL)‐6, IL‐10, and tumor necrosis factor‐α (TNF‐α) in their BALF (all p < .05). (3) The proportions of neutrophils and macrophages in the BALF of the High MP‐DNA MPP and Fever MPP groups increased and decreased, respectively (all p < .05). (4) In the BALF of MPP children, MP‐DNA, IL‐6, IL‐10, TNF‐α, and interferon gamma (IFN‐γ) levels positively correlated with neutrophil proportion while negatively correlated with macrophage proportion (all p < .05). (5) The MP‐DNA, IL‐6, IL‐10, TNF‐α, and IFN‐γ levels in the BALF of MPP children were positively correlated with the levels of C‐reactive protein, procalcitonin, lactic dehydrogenase, fibrinogen, and d‐dimer, while they were negatively correlated with the albumin level (all p < .05). CONCLUSIONS: In children with MPP, the pulmonary inflammatory immune response was stronger in the High MP‐DNA MPP, Fever MPP, Fervescence MPP, and Severe MPP groups. The relationship between pulmonary cytokine levels, MP‐DNA load, and serum inflammatory parameters were found to be weak.