Prevalence and clinical outcomes of fibrotic interstitial lung disease in ANCA associated vasculitis: a single-centre, retrospective, cohort study

Background: antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) may affect multiple organs and interstitial lung disease (ILD) might be the first manifestation. Limited and discordant data are available on the prevalence of ILD in patients with AAV. Little is known about prognostic outcomes of these patients. The primary aim of the study was to determine the prevalence of fibrotic ILD in a cohort of AAV patients followed-up in a University Hospital in Italy. Clinical and prognostic outcomes of AAV-ILD were also assessed. Methods: Data from 71 AAV patients (mean age 60.3  16 years; female 58.9%) were retrospectively collected and analyzed. Results: Overall ILD prevalence was 50.7%. Fibrotic ILDs represented 32.4% with a variable distribution according to diagnosis: microscopic polyangiitis (MPA) 66.7%, eosinophilic granulomatosis with polyangiitis (EGPA) 41.1%, granulomatosis with polyangiitis (GPA) 31.8%. The presence of ILD was significantly different across AAV subgroups. Fibrotic ILD was more prevalent in MPA (60%) than EGPA (11.8%) and GPA (9.1%) and most frequently associated with usual interstitial pneumonia (UIP) pattern. The presence of ANCA was significantly associated with fibrotic ILDs (p=0.01). In univariate analysis only MPA increased the risk of having ILD (OR 2 (CI 95%: 0.96-4.67). Mortality was significantly higher in patients with ILD (p=0.01), with fibrotic forms influencing this finding and MPA showing the highest mortality. Conclusions: Fibrotic ILDs are common in patients with AAV and influence clinical and prognostic outcomes. MPA is the most frequent AAV associated to fibrotic ILD. ILD should be investigated at diagnosis in all patients with AAV, since early diagnosis might impact the prognosis of these patients.