Thoracic Manifestations of ANCA-associated Vasculitis: Review of the 2022 American College of Rheumatology-European Alliance of Associations of Rheumatology Classification Criteria

Abstract

Antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) is a rare disease that manifests as necrotizing vasculitis involving small vessels without immune complex deposition. Granulomatosis with polyangiitis (GPA), eosinophilic granulomatosis with polyangiitis (EGPA), and microscopic polyangiitis (MPA) are included in this disease entity. Diagnosis and differentiation of AAV is challenging because of the diverse and overlapping clinical manifestations and lack of pathognomonic findings. Therefore, AAV classification criteria have been developed to increase the likelihood of diagnosis using multidisciplinary approaches, including clinical, radiologic, laboratory, and pathologic findings. The new American College of Rheumatology and European Alliance of Associations for Rheumatology classification criteria were released in 2022 to classify AAVs using weighted criteria and threshold scores. They are expected to make the classification of GPA, EGPA, and MPA more accurate in the setting of suspected small-vessel vasculitis. The criteria present key thoracic imaging discriminators of GPA as pulmonary nodules, masses, or cavitation and MPA as interstitial fibrosis, whereas, radiologic criteria of EGPA are not present. ANCA positivity and eosinophil count are included as key laboratory discriminators. It is essential for radiologists to familiarize themselves with imaging findings of each AAV and know the key imaging discriminators to aid in the differential diagnosis of AAVs. By reviewing the radiologic findings of thoracic manifestations of each AAV and applying the new criteria in a series of cases, the authors aim to provide a practical and stepwise approach to AAV for radiologists.