Association Between Bronchiectasis and Serious Infections in Microscopic Polyangiitis and Granulomatosis With Polyangiitis From the J‐ CANVAS

BACKGROUND: Bronchiectasis is known to be more frequently observed in patients with microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA) compared to the general population. However, its association with patient outcomes and the potential influence of immunosuppressive treatment on this association remain unclear. METHODS: We conducted a multicenter observational study using data from the Japan Collaborative Registry of ANCA-Associated Vasculitis (J-CANVAS). Adult patients with newly diagnosed or relapsing MPA or GPA between January 2017 and March 2023 were included. The exposure was clinically apparent bronchiectasis at baseline. Primary outcomes were serious infections and all-cause mortality; relapses were examined as a secondary outcome over 52 weeks. For each outcome, incidence rate ratios (IRRs) were estimated using multivariable Poisson regression models conditioned on confounding factors, incorporating follow-up time as an offset term. Interactions between initial treatment (prednisone dose, rituximab, cyclophosphamide, intravenous methylprednisolone, and plasma exchange) and bronchiectasis were also evaluated. RESULTS: Among 844 patients (MPA: 614; GPA: 230), 68 (8.1%) had bronchiectasis. During the follow-up period, there were 122 serious infections among 101 patients, 48 deaths, and 85 relapses among 72 patients. Adjusted IRRs for patients with bronchiectasis were 2.18 (95% CI: 1.25-3.83) for serious infections, 3.07 (1.41-6.66) for mortality, and 1.58 (0.77-3.24) for relapse. No clear interaction was detected between specific treatments and bronchiectasis. CONCLUSIONS: Bronchiectasis was associated with increased risks of serious infections and mortality in patients with MPA and GPA. However, we did not detect clear interaction by initial treatment, suggesting that avoiding specific therapies may not be necessary.