Fig. 2

The representative computed tomography images of four groups. a usual interstitial pneumonia; b non-specific interstitial pneumonia; c organizing pneumonia; d pulmonary granuloma; e alveolar haemorrhage; f small airway involvement; g tracheobronchial stenosis. a An 81-year-old male came to the department of respiratory with progressive dyspnea and was found to be MPO-ANCA positive and diagnosed with MPA. The chest CT manifested fibrotic changes of UIP pattern in basal and subpleural predominance, traction bronchiectasis, and honeycombing. b A 56-year-old male came to the nephrology department with elevated serum creatinine on physical examination. He was MPO-ANCA positive and diagnosed with MPA. CT scan showed peripheral ground-glass opacity and typical subpleural sparing representing the NSIP pattern. c A 58-year-old female visited the respiratory department due to a persistent cough. She was MPO-ANCA positive and diagnosed as MPA. CT presented bilateral peribronchovascular and peripheral patchy consolidations combined with reversed halo sign, which is typical for OP. d A 65-year-old female came to the rheumatology department with multisystem involvement symptoms, including cough and hemoptysis. She was MPO-ANCA positive and diagnosed with GPA. CT showed bilateral nodules and consolidations, combined with cavitation. e A 47-year-old male visited the respiratory department due to hemoptysis and other multisystem symptoms. He was PR3-ANCA positive and diagnosed with GPA. CT demonstrated diffuse ground-glass attenuation in the left side. f A 58-year-old female visited the respiratory department with cough and sinusitis. She was both MPO-ANCA and PR3-ANCA positive and diagnosed with GPA. CT manifested as bilateral centrilobular nodules, regarded as the typical tree-in-bud sign. g A 27-year-old female was admitted to the respiratory department due to severe dyspnea. She was PR3-ANCA positive and diagnosed as GPA. CT showed tracheobronchial stenosis