A closer look to the lung involvement in ANCA-associated vasculitis: alveolar haemorrhage and interstitial lung disease

Interstitial lung disease (ILD) and alveolar haemorrhage (AH) have been described as possible pulmonary involvements associated with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), mainly granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA). To evaluate the clinical, laboratory and demographic features of ANCA positivity in AAV; in particular, we aimed to determine the criteria predicting ILD involvement and AH. This study was designed as a cross-sectional and retrospective study conducted in a single centre. The studies comprised 83 individuals in total who were routinely followed at a tertiary rheumatology clinic between June 2016 and February 2024. A total of 83 patients consisting of 56 GPA (67.4%), 22 MPA (26.5%) and 5 ANCA-negative (6.1%) cases were included in the study. When adjusted for age and sex in a multivariate regression model, the correlation of AH with C-ANCA was confirmed (OR 4.80; 95% CI 1.29-17.91) (p = 0.020). The subsequent multivariate regression analysis reveals that the P-ANCA variable significantly predicts ILD (OR 4.28; 95% CI 1.25-14.65) (p = 0.021) when adjusted for age and sex. AH was found to be higher in patients with GPA and in patients with C-ANCA positivity. It was shown that P-ANCA positivity predicted ILD involvement in AAV patients. The widespread ILD involvement observed in P-ANCA-positive patients confirmed usual interstitial pneumonia, but nonspecific interstitial pneumonia was also found to predominate in C-ANCA-positive and ANCA-negative cases.