[Anti-neutrophil cytoplasmic antibody-positive interstitial lung disease: rethinking classification from a...

Anti-neutrophil cytoplasmic antibodies (ANCA) positivity is not uncommon among patients with interstitial lung disease(ILD), but its clinical significance and disease classification remain poorly defined. Some patients present only with pulmonary fibrosis and show no evidence of systemic vasculitis throughout long-term follow-up, whereas others gradually develop ANCA-associated vasculitis (AAV). Current classification systems generally place such cases in the categories of AAV-associated ILD, ANCA-positive ILD, or interstitial pneumonia with autoimmune features (IPAF). However, none of these categories adequately accounts for their marked clinical heterogeneity and dynamic evolution. Recent studies suggest that ANCA-associated interstitial lung involvement may represent a disease spectrum linking pulmonary fibrosis and systemic vasculitis rather than a discrete disease entity with well-defined boundaries. Drawing on relevant research advances, this commentary examines the challenges in classifying ANCA-positive ILD and reconsiders its clinical significance from the perspectives of disease spectrum and dynamic evolution. Such an approach may provide a more comprehensive framework for understanding its biological heterogeneity and clinical behavior.