For patients with definite UIP and MPO-ANCA-associated vasculitis limited to the lungs (without systemic manifestations), what is the role of immunosuppression?

I think in these subjects (as opposed to UIP in RA), immune suppression would be my first agent. The data are limited; there is some suggestion on biopsy that they have significant inflammation (Arnold et al., PMID 38574743). I would start with immunosuppression and have a low threshold to add anti-fibrotic because we think that there are patients who have progressive fibrosis once they crossed some extent threshold, even if you remove the inflammation that's driving it.