[Clinical Phenotyping of Severe Pneumonia in Children]

To investigate and summarize pediatric patients with severe pneumonia (MPP) presenting with varied clinical and chest imaging features in order to guide the individualized treatment. This was a retrospective cohort study. Medical records of clinical, imaging and laboratory data of 505 patients with MPP who were admitted to the Department Ⅱ of Respirology Center, Beijing Children's Hospital, Capital Medical University from January 2016 to October 2023 and met the enrollment criteria were included. They were divided into severe group and non-severe group according to whether lower airway obliterans was developed. The clinical and chest imaging features of the two groups were analyzed. Those severe cases with single lobe ≥2/3 consolidation (lobar consolidation) were further divided into subtype lung-necrosis and subtype non-lung-necrosis based on whether lung necrosis was developed. Comparison on the clinical manifestations, bronchoscopic findings, whole blood C-reactive protein (CRP) and other inflammatory indicators between the two subtypes was performed. Comparisons between two groups were achieved using independent-sample -test, nonparametric test or chi-square test. Univariate receiver operating characteristic (ROC) curve analyses were performed on the indicators such as CRP of the two subtypes. Of the 505 cases, 254 were male and 251 were female. The age of the onset was (8.2±2.9) years. There were 233 severe cases, among whom 206 were with lobar consolidation and 27 with diffuse bronchiolitis. The other 272 belonged to non-severe cases, with patchy, cloudy infiltrations or single lobe <2/3 uneven consolidation or localized bronchiolitis. Of the 206 cases (88.4%) severe cases with lobar consolidation, 88 harbored subtype lung-necrosis and 118 harbored subtype non-lung-necrosis. All 206 cases (100.0%) presented with persistent high fever, among whom 203 cases (98.5%) presented with inflammatory secretion obstruction and plastic bronchitis under bronchoscopy. Of those 88 cases with subtype lung-necrosis, there were 42 cases (47.7%) with dyspnea and 39 cases (44.3%) with moderate to massive amount of pleural effusion. There were 35 cases (39.8%) diagnosed with lung embolism during the disease course, of which other 34 cases (38.6%) were highly suspected. Extensive airway mucosal necrosis was observed in 46 cases (52.3%), and the level of their whole blood CRP was significantly higher than that of subtype non-lung-necrosis (131.5 (91.0, 180.0) 25.5 (12.0, 43.1) mg/L, =334.00, <0.001). They were regarded as subtype "lung consolidation-atelectasis-necrosis". Of those 118 cases with subtype non-lung-necrosis, 27 cases (22.9%) presented with dyspnea and none were with moderate to massive amount of pleural effusion. Sixty-five cases (55.1%) presented with plastic bronchitis and localized airway mucosal necrosis was observed in 32 cases (27.1%). They were deemed as subtype "lung consolidation-atelectasis". ROC curve analyses revealed that whole blood CRP of 67.5 mg/L on the 6-10 th day of disease course exhibited a sensitivity of 0.96, a specificity of 0.89, and an area under the curve of 0.97 for distinguishing between these two subtypes among those with lobar consolidation. Pediatric patients with severe MPP present with lobar consolidation or diffuse bronchiolitis on chest imaging. Those with lobar consolidation harbor 2 subtypes as "lung consolidation-atelectasis-necrosis" and "lung consolidation-atelectasis". Whole blood CRP of 67.5 mg/L can be applied as an early discriminating indicator to discriminate between these two subtypes.