To investigate the clinical and imaging manifestations of the respiratory system in children with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV).

The clinical and imaging manifestations of the respiratory system as well as laboratory data of 25 AAV children who were treated from June 2014 to June 2018 at Department of Paediatrics, Jinling Hospital, School of Medicine, Nanjing University were analyzed.

The main clinical manifestations of the respiratory system in children with AAV were proliferation of lymphoid follicles on the posterior pharyngeal wall, rales in the lungs, and fever. After treatment, white blood cell count, neutrophil count, erythrocyte sedimentation rate, procalcitonin, interleukin-6, mycoplasma IgM antibody, respiratory syncytial virus IgM antibody, and the number of Streptococcus pneumoniae in urine were significantly decreased (P＜0.05 or P＜0.01), while complement C3, IgE, IgG, CD4⁺ T cells, CD3⁺ T cells, and CD8⁺ T cells were significantly increased (P＜0.05 or P＜0.01). Chest CT showed that 20 cases had lung injuries, most of which were bilateral. The imaging findings included patchy and flocculent high density shadows, accompanied by pleural effusions and lymph node enlargement. Follow-up of the 25 AAV children showed that one died and three had entered ESRD stage. The 1-year and 2-year kidney survival rates after renal biopsy were 93.33% and 77.78%, respectively. The cumulative survival rates at 1 and 2 years were both 93.33%.

Respiratory system manifestations appear early in the clinical manifestations of AAV in children, but lack specificity. Lung imaging examination can show multiple lesions, which also lack specificity. Complements and cellular immunity are involved in the pathogenesis and development of AAV.