Isolated antineutrophil cytoplasmic antibody-associated interstitial lung disease: A systematic review of an emerging...

To summarise the clinical characteristics, radiological and histopathological features, treatment approaches, and outcomes of isolated antineutrophil cytoplasmic antibody-associated interstitial lung disease (ANCA-ILD).

A systematic literature review conducted according to the PRISMA statement.

Twenty-four studies comprising 794 patients were included. Isolated ANCA-ILD predominantly affected older adults, between 50 and 70 years of age, with a slight male predominance (57%). MPO-ANCA positivity was observed in approximately 70% of patients, whereas PR3-ANCA positivity accounted for 10-15%. Fibrotic patterns predominated, with usual interstitial pneumonia (UIP) or UIP-like changes reported in 45-65% of cases, followed by NSIP in 15-30%. Glucocorticoids were prescribed in 58% of patients, immunosuppressive therapies in 31%, and antifibrotic treatment in approximately 26% of those reported in more recent cohorts. Functional decline occurred in approximately 30-50% of patients, and radiological progression in 30-45%. Acute exacerbations were reported in 19-25%, and up to 40% fulfilled criteria for progressive pulmonary fibrosis during follow-up. Progression to systemic ANCA-associated vasculitis (AAV) occurred in approximately 10-40% of cases, with timing ranging from the first year to several years later. This evolution occurred mainly toward microscopic polyangiitis (MPA), whereas granulomatosis with polyangiitis was infrequent, representing ≤10-20% of cases. Survival was generally comparable to ANCA-negative idiopathic interstitial pneumonia and AAV-ILD.

Isolated ANCA-ILD is an emerging, increasingly recognised fibrotic interstitial lung disease phenotype characterised by frequent MPO-ANCA positivity and two partly independent trajectories: (1) an IPF-like fibrotic course and (2) progression to systemic AAV, most commonly MPA.