New study shows fibrotic ILD common in patients with AAV

Fibrotic interstitial lung disease (ILD) is common among patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and is associated with worse clinical outcomes, including higher mortality, according to a study by Italian researchers.

The study, published Feb. 17 in Respiratory Research, evaluated the prevalence, clinical characteristics and outcomes of fibrotic ILD in patients with AAV.

Led by Claudio Tirelli, M.D., at the Università Degli Studi Di Milano in Milan, the researchers looked to better define how frequently ILD occurs in this population and how it affects prognosis, an area where prior data have been limited and inconsistent.

AAV is a group of rare systemic autoimmune diseases that affect small- to medium-sized blood vessels and can involve multiple organs, including the lungs. The pulmonary manifestations are are known, but the prevalence and prognostic impact of ILD in this population have not been fully characterized.

To address this gap, the researchers conducted a retrospective observational cohort study of 71 patients with AAV followed at a single center in Italy. The cohort had a mean age of approximately 60 years, and nearly 59% were female.

Overall, ILD was identified in just over half of patients, with a prevalence of 50.7%. Fibrotic ILD, which represents the more advanced and clinically significant form of disease, was present in 32.4% of the cohort.

The prevalence of fibrotic ILD varied significantly depending on the subtype of AAV, the researchers noted. It was most common in patients with microscopic polyangiitis (MPA), where fibrotic ILD was observed in approximately 60% of cases. Meanwhile, fibrotic ILD was less frequent in eosinophilic granulomatosis with polyangiitis (EGPA) and granulomatosis with polyangiitis (GPA), occurring in 11.8% and 9.1% of patients, respectively.

Radiologically, the usual interstitial pneumonia pattern was the most frequently observed imaging phenotype among patients with fibrotic ILD. The presence of ANCA positivity was significantly associated with fibrotic ILD, further supporting a link between autoimmune activity and fibrotic lung involvement

In terms of risk factors, univariate analysis identified MPA as the only AAV subtype associated with an increased likelihood of ILD, although the confidence interval suggested some uncertainty in the estimate.

Notably, the presence of ILD was associated with worse outcomes. Mortality was higher among patients with ILD compared with those without lung involvement, and fibrotic forms of ILD appeared to drive this increased risk. Patients with MPA, who had the highest prevalence of fibrotic ILD, also experienced the highest mortality rates in the cohort.

The findings by the Milan team reinforce the clinical significance of lung involvement in AAV and suggest that fibrotic ILD represents a key determinant of prognosis. The results are consistent with prior studies indicating that pulmonary fibrosis in autoimmune diseases can contribute to progressive respiratory decline and increased mortality risk.

The authors noted that ILD may represent an early or even initial manifestation of AAV in some patients, underscoring the importance of early recognition. Because pulmonary involvement may be asymptomatic or subtle in early stages, routine screening for ILD at the time of AAV diagnosis could improve detection and allow for earlier management.

“ILD should be investigated at diagnosis in all patients with AAV,” wrote Tirelli and his co-authors, noting that early identification may influence clinical outcomes.

The study has several limitations, including its retrospective design and relatively small sample size, as well as its single-center setting, which may limit generalizability. Additionally, variability in disease presentation and treatment approaches across patients could influence outcomes.

Despite these limitations, the findings provide important real-world insight into the burden of fibrotic ILD in AAV and highlight the need for greater awareness of pulmonary involvement in this patient population.

According to the researchers, the study underscores the importance of considering ILD as part of the disease spectrum in AAV and supports a more proactive approach to screening and monitoring.