An Atypical Case of Antineutrophil Cytoplasmic Antibody (ANCA)-Associated Vasculitis With Isolated Lower Airway Involvement in a Young Adult

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV) typically present in middle-aged adults with multiorgan involvement.We describe the case of a 19-year-old woman with asthma, progressive dyspnea, and recurrent bronchial stenosis and webbing.Serological testing showed rising perinuclear ANCA (p-ANCA) and anti-myeloperoxidase (MPO) antibody titers, whereas cytoplasmic ANCA (c-ANCA) and antiproteinase 3 (PR3) antibodies were negative.Biopsy revealed nonspecific inflammation and fibrosis.Infectious causes, malignancy, relapsing polychondritis, and sarcoidosis were excluded.Although the presentation did not meet the 2022 American College of Rheumatology/European Alliance of Associations for Rheumatology (ACR/EULAR) classification criteria threshold for granulomatosis with polyangiitis (GPA), which are intended for research classification rather than clinical diagnosis, bronchial-limited AAV, most consistent with GPA, was considered the working diagnosis.The patient improved following corticosteroid treatment and bronchoscopic dilation.