A Descriptive Register of ANCA ‑ Positive Vasculitis Patients with Kidney Involvement: A Portuguese Center Experience over 13 Years

Introduction: Anti­‑neutrophil cytoplasm antibody (ANCA)­‑associated vasculitis (AAV) is a necrotizing disease affecting small blood vessels, commonly involving the kidneys, and associated with high morbidity and mortality. Methods: We conducted a descriptive cross­‑sectional study at Hospital de São João in Porto, including patients aged 18 or older with biopsy­‑proven kidney involvement from AAV, followed by a multidisciplinary team from December 2010 to June 2023. We analyzed demographic, clinical, and laboratory variables, kidney pathology findings, treatment regimens, and patient outcomes. Results: Fifty­‑one patients were included, with a median age of 66 years (IQR, 56­‑74) and a male predominance (61%). Most patients (78%) had myeloperoxidase (MPO)­‑associated AAV. Chronic kidney disease (CKD) was present in 18% of cases, and 96% presented with rapidly progressive glomerulonephritis (RPGN). Hemodialysis was required in 29% of cases. Induction therapy consisted of cyclophosphamide and glucocorticoids in 86%, with a median cyclophosphamide dose of 6 g (IQR, 3.25­‑8.25). After 2020, five patients received rituximab plus glucocorticoids. Plasma exchange was performed in 12 patients (nine with alveolar hemorrhage). Maintenance therapy included azathioprine in 32 patients and rituximab in six patients. Of patients requiring hemodialysis, 40% recovered kidney function. During follow­‑up, 39% of patients progressed to end­‑stage kidney disease, ten patients (20%) relapsed, and 17 died (33%). Conclusion: This study provides valuable insights into the epidemiology, treatment, and outcomes of AAV with kidney involvement in Portugal. Further studies are needed to optimize treatment strategies across more centers.