Background/Purpose: ANCA-associated vasculitis (AAV) are heterogeneous disorders with a clinical presentation that may range from a full-blown disease to incomplete forms with isolated organ involvement. In particular, interstitial lung disease (ILD) may represent the only clinically evident involvement in some patients. Aim of our work was to describe AAV patients with isolated ILD focusing on their clinical characteristics, long-term outcome and clinical-serological associations.

Methods: In this single center study we collected epidemiologic, demographic, clinical, laboratory and serological data of AAV patients, excluding patients with diagnosis of EGPA. We recorded disease activity at the disease onset by Birmingham Vasculitis Activity Score (BVAS) and damage by using the Vasculitis Damage Index (VDI).

Results: Fifty-four patients with AAV (M:F=32:22, mean age at diagnosis 55.1±5.2 years) were enrolled. Twenty-nine patients were ANCA-MPO positive, while 25 were ANCA-PR3 positive. Eight ANCA positive patients (8/54, 14.8%) presented ILD as the main clinical feature of AAV (5 ILD as the only manifestation). The ILD pattern at lung CT was “non-specific interstitial pneumonia” (NSIP)-like in 2 patients and “usual interstitial pneumonia” (UIP)-like in 6 cases. Seven patients were ANCA-MPO positive while 1 was ANCA-PR3 positive. ILD patients presented a higher mean age at the disease onset compared to non-ILD subjects (65.63±7.36 vs 53.3±15.49 p=0.04), lower creatinine values (0.78 ±0.13 vs 1.77±2.1 p=0.018) and a lower BVAS at the disease onset (BVAS 3.75 ± 2.49 vs 13.71±6.7 p=0.013). In the long-term follow-up (mean follow-up: 8.31±9.24 years), none of the ILD patients presented an end-stage renal disease (vs 6 in non-ILD patients) or disease flares (vs 26 in non-ILD cases). The final VDI was lower in ILD patients when compared to non-ILD patients (VDI 2.12±0.83 vs 3.71±2.41 p=0.004). Moreover, no deaths were observed in the ILD group (vs 7 in non-ILD).

Conclusion: Patients with AAV presenting ILD seem to present a different phenotype compared to patients with a complete form of AAV. ILD patients presented lower disease activity at the onset, lower prevalence of complications, lower damage and an a overall better prognosis compared to non-ILD patients. Further prospective studies in larger cohorts may clarify whether patients with isolated ILD should be classified as a distinct subset or an incomplete form of AAV.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/interstitial-lung-disease-in-anca-associated-vasculitis-a-distinct-or-an-incomplete-subset-in-anca-vasculitis-patients/