Background/Purpose: ANCA-associated vasculitides (AAV)—granulomatosis with polyangiitis (GPA), eosinophilic granulomatosis with polyangiitis (EGPA), and microscopic polyangiitis (MPA)are rare but severe systemic vasculitides with significant morbidity and mortality. Existing epidemiological data in Spain are limited to specific regions, hindering comprehensive national understanding.Purpose: to estimate the incidence of AAV in Spain and describe its clinical, analytical, histopathological, and prognostic features, treatment patterns, and long-term outcomes.

Methods: Retrospective, multicenter cohort study involving 32 hospitals across Spain. Patients ≥18 years with newly diagnosed AAV between January 1,2015and March 31, 2021, were included. Data were extracted from medical records and entered into a centralized electronic database. The follow-up period ensured a minimum follow-up of 15 months for each patient. Incidence rates were calculated based on the adult population within each center’s reference area. Disease activity, organ damage, and outcomes were assessed using validated scores (BVAS, FFS, VDI).

Results: 840 patients were included (53.7% women; median age 66 years).(Table 1) After excluding patients who did not reside within the reference area of the hospital where they were treated, 695 patients were included in the incidence análisis. For the analysis of clinical characteristics, all patients were included (N = 840).MPA was the most frequent subtype (51%), followed by GPA (26.8%) and EGPA (13.7%). Most patients (84%) fulfilled the 2022 ACR/EULAR classification criteria. The cumulative incidence was 70.3 cases per million adults (95% CI: 65.1–75.6) over the study period, and the overall annual incidence was 11.3 (95% CI: 10.4–12.1) cases per million adults. By vasculitis subtype, the annual and cumulative incidence was: MPA: anual 5.7 (95% CI: 5.2–6.3); cumulative: 35.8 per million(95% C: 32,2-39,6). GPA: anual 3.0 (95% CI: 2.3–3.5); cumulative: 18.8 per million (95% CI: 16,2-21,5). EGPA: anual 1.6 (95% CI: 1.3–1.9); cumulative: 10.0 per million (95% CI: 8,1-12). (Table 2). At diagnosis, 70.3% of patients had renal involvement and 64.4% were MPO-ANCA positive. The median BVAS at diagnosis was 15.0 [12.0, 20.0]. The median Five-Factor Score (FFS) at diagnosis was 1.0 [1.0, 2.0]. Biopsies were performed in 79.7% of patients, with 68.4% confirming AAV-compatible histopathology. During follow-up, 35.4% experienced relapse, 42.2% achieved remission. 17.1% died; death was higher in men (p=0.006) (main causes of death were infections and active disease). Median Vasculitis Damage Index (VDI) increased from 2.0 at 6 months to 3.0 at the end of follow-up. General information and lifestyle habits are shown in table 3.

Conclusion: This is the largest AAV registry in Spain to date and the first to provide national incidence estimates. The findings confirm MPA as the predominant subtype followed by GPA and EGPA. Mortality was higher in men than in women

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/incidence-and-clinical-characteristics-of-anca-associated-vasculitis-a-nationwide-study-in-spain/