Introduction
Usual interstitial pneumonia (UIP) pattern is a necessary but not sufficient condition to diagnose Idiopathic pulmonary fibrosis (IPF) and the most common radiological finding in pulmonary Microscopic Polyangitis (MPA)(Kadura et al., 2021).  Only positivity for p-ANCA is not enough to classificate an ILD secondary to a systemic vasculitis, but biopsy or clinical evidence of it allows a Microscopic Polyangitis (MPA) diagnosis(Suppiah et al., 2022).

Aims
In a cohort of IPF patients with positivity for p-ANCA, we investigated about features and differences compared to an IPF group.

Methods
We retrospectively recruited 18 patients with IPF and p-ANCA positivity at the baseline or during the follow-up, comparing them to a control group formed by consecutive IPF patients, in a 2:1 proportion (n:36), matched for age and sex. FVC, DLCO and 6 minutes walking test distance (6MWD) at the baseline and after 1 year and serologic testing for autoimmune diseases were collected.

Results
Among the two groups (mean age 68.83±7.2;  66% Male), there was no statistically significance difference in FVC, DLCo and 6MWD at the baseline and at 1 year. In the p-ANCA group, 9 patients (50%) developed vasculitis (5 renal involvement, 4 cutaneous) and 10 patients met criteria for diagnosis of MPA (55.5%). Higher level of rheumatoid factor (RF) was predictive of vasculitis onset (p=0,23, X2 5,14).

Conclusions
IPF patients with positivity for p-ANCA have similar characteristics and evolution of IPF patients. These patients have a higher risk of vasculitis after the ILD onset; for this reason, a careful evaluation is needed during follow up, especially for possible life-threating other organ involvement.