What are the clinical features of small airway disease in AAV patients?

One unique indicator of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV)-related lung involvement is small airway disease (SAD), which has distinct clinical features, reports a study.

In this study, the authors recorded SAD when the manifestations of either centrilobular nodules or air trapping were observed according to computed tomography (CT) scans, except for infection or other airway-related comorbidities. They also collected baseline and follow-up data retrospectively.

A total of 359 patients had a diagnosis of AAV with pulmonary involvement. Of these, 92 (25.6 percent) had SAD, including 79 (85.9 percent) antimyeloperoxidas (MPO)-ANCA-positive, nine (9.8 percent anti-PR3-ANCA positive, and two (2.2 percent) double positive cases.

SAD patients tended to be younger, female, nonsmokers, have more ear-nose-throat (ENT) involvement, and higher baseline Birmingham Vasculitis Activity Score (BVAS) relative to those without SAD. Several patients with AAV-related SAD showed improved lung function and CT scans following immunosuppressive therapy.

Compared with patients without SAD, those with SAD exhibited better prognosis. When dividing patients into groups (isolated SAD [only small airway involvements], SAD with other lower airway involvements, and non-SAD), those in the SAD with lower airway involvement group had the greatest risk of infection. On the other hand, patients in the non-SAD group suffered from the worst long-term outcomes.

Subgroup analyses revealed similar findings in anti-MPO-ANCA positive patients.

“It is vital to focus on SAD because of its association with prognosis and infection in AAV patients, especially in anti-MPO-ANCA positive patients,” the authors said. “Moreover, SAD might represent a better response to immunosuppressors.”