The effect of pulmonary nodule presence on disease severity and course in ANCA-associated vasculitis: a multicenter cohort study

Pulmonary nodules are common in ANCA-associated vasculitis (AAV), but their clinical relevance remains unclear. This study assessed the influence of pulmonary nodules and radiological features on clinical characteristics and outcomes in AAV. In this multicenter retrospective cohort, clinical features and outcomes were compared between nodule-positive and nodule-negative AAV patients. Pulmonary nodules were classified as cavitary or non-cavitary, and their morphology and regression were evaluated on serial CT scans at diagnosis, 6 months, and last follow-up. Among patients with pulmonary nodules, radiological regression rates were compared according to cavitary and non-cavitary nodule status. Associations between radiological parameters, inflammatory markers, and radiological outcomes were evaluated using correlation analyses. Among 342 patients, 100 had pulmonary nodules at diagnosis (51 cavitary, 49 non-cavitary). Patients presenting with pulmonary nodules at diagnosis more likely to have lower baseline proteinuria, a higher prevalence of pleural effusion, and an increased risk of pulmonary nodule relapse (p = 0.043, p = 0.022, and p < 0.001, respectively). Radiological regression rates did not differ between cavitary and non-cavitary nodules at 6 months or last control. Moreover, smaller cavitary nodule diameter, a lower necrosis ratio, and fewer cavitary nodules were associated with a higher rate of complete radiological regression at 6 months (p = 0.016, p < 0.001, and p = 0.046, respectively). Larger cavitary nodule diameter and increased wall thickness correlated with elevated CRP levels (p = 0.001, r = 0.452 and p = 0.018, r = 0.340, respectively). In AAV, cavity size and wall thickness were associated with systemic inflammation. A lower necrosis ratio, smaller cavity diameter, and fewer cavitary nodules were associated with favorable radiological outcomes. These exploratory findings require prospective validation using standardized CT protocols. 1. Patients presenting with pulmonary nodules at diagnosis had a higher risk of pulmonary nodule relapse. 2. Larger cavity diameter and greater wall thickness were associated with higher systemic inflammatory activity. 3. A lower necrosis ratio, smaller cavity diameter, and fewer cavitary nodules were associated with complete radiological regression.