Pulmonary and Renal Predictors of Mortality in ANCA-Associated Vasculitis: A Regional Experience from Türkiye

<b>Background/Objectives</b>: Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is a rare autoimmune disease marked by small-vessel inflammation. Pulmonary and renal manifestations are believed to critically influence prognosis, but detailed regional data are lacking. This study aimed to determine the prevalence and prognostic impact of pulmonary and renal involvement in AAV patients in the Thrace region of Türkiye. <b>Methods</b>: A retrospective cohort study was conducted on 78 biopsy-proven AAV patients followed between 2018 and 2025. Demographic, clinical, laboratory, and outcome data were analysed. Logistic regression identified predictors of relapse and mortality. <b>Results</b>: The cohort included 44 granulomatosis with polyangiitis, 30 microscopic polyangiitis, and 4 eosinophilic granulomatosis with polyangiitis patients; 40 were pr3-ANCA positive and 33 MPO-ANCA positive. Pulmonary involvement was observed in 71.8% and renal involvement in 74.4%, and overall mortality was 20.5%. All deaths occurred in patients with pulmonary involvement (28.6% vs. 0%, <i>p</i> = 0.048). Relapse was higher in those with pulmonary (17.9% vs. 4.5%, <i>p</i> = 0.048) and renal (15.5% vs. 5%, <i>p</i> = 0.056) involvement. Multivariate analysis showed that pulmonary involvement (OR 3.82, <i>p</i> = 0.002), renal involvement (OR 4.73, <i>p</i> = 0.013), and rituximab treatment (OR 10.79, <i>p</i> = 0.049) predicted relapse; elevated CRP (OR 1.01, <i>p</i> = 0.003), creatinine (OR 1.42, <i>p</i> = 0.028), hypoalbuminaemia (OR 0.24, <i>p</i> = 0.046), renal (OR 2.86, <i>p</i> = 0.031), and pulmonary (OR 3.21, <i>p</i> = 0.003) involvement predicted mortality. <b>Conclusions</b>: Pulmonary and renal involvement are highly prevalent and represent the strongest predictors of relapse and mortality in AAV patients in this regional cohort. Recognising these risks is essential to guide early interventions and improve patient outcomes.