Interstitial lung disease in microscopic polyangiitis and granulomatosis with polyangiitis: demographic, clinical, serological and radiological features of an Italian cohort from the Italian Society for Rheumatology.

Interstitial lung disease (ILD) has been described as a possible pulmonary involvement in antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitides (AAV), mainly granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA). Aim of this cross-sectional Italian national study was to describe demographic, clinical and serological profile of ILD related to MPA and GPA and investigate possible correlations between radiologic patterns of ILD and vasculitis features. We enrolled 95 consecutive patients with AAV-ILD, 56 affected by MPA (58.9%) and 39 by GPA (41.1%). NSIP was the most frequently detected ILD pattern, observed in c-ANCA patients in 60.9% of cases, followed by UIP pattern mainly observed in p-ANCA patients (47.7%, p=0.03). ILD represented the first clinical manifestation, preceding vasculitis diagnosis in 22.1% of cases and, globally, ILD was already detectable at AAV diagnosis in 66.3% of patients. The diagnosis of ILD preceded that of AAV in 85.7% of p-ANCA positive-patients, while only one patient with c-ANCA developed ILD before AAV (p= 0.039). Multivariate analysis confirmed the correlation of UIP pattern with p-ANCA-positivity and a diagnosis of ILD before AAV, also when adjusted for age and sex. Our study confirms that UIP is a frequent pattern of lung disease in AAVILD patients. Our results also suggest that ILD can represent an early complication of AAV but also occur in the course of the disease, suggesting the need of a careful evaluation by both pulmonologist and rheumatologist to achieve an early diagnosis. Further prospective studies are needed to define ILD prevalence and evolution in AAV patients.