Antineutrophil Cytoplasmic Antibody-Associated Lung Fibrosis

Pulmonary fibrosis is observed in a substantial number of patients with ANCA-associated vasculitis (AAV), 15% in a recent German series, and may be more frequent in Asian populations. ANCA are usually of anti-MPO specificity and microscopic polyangiitis is the most frequent vasculitis. Pulmonary fibrosis may increase the risk of death in patients with AAV. Treatment for AAV in patients with lung fibrosis should follow the international guidelines for vasculitis. The role of anti-fibrotic drugs (pirfenidone, nintedanib) in this condition is still unknown. Pulmonary fibrosis precedes the diagnosis of AAV or is diagnosed concomitantly in most of the cases. Interestingly, 4% to 35% of patients with pulmonary fibrosis are ANCA-positive, but only 7% to 23% of the patients with pulmonary fibrosis and anti-MPO will develop AAV during follow-up. ANCA positivity may be detected in idiopathic or non idiopathic pulmonary fibrosis. In the absence of vasculitis, the detection of ANCA does not influence the diagnostic work-up of patients with lung fibrosis. If an Idiopathic Pulmonary Fibrosis diagnosis is considered, an anti-fibrotic therapy should be considered, according to local and international guidelines.