Diffuse pulmonary lesions caused by ANCA-associated vasculitis: A case report

Rationale: Anti-neutrophil cytoplasmic antibody–associated vasculitis (AAV) encompasses rare, multisystem autoimmune diseases such as granulomatosis with polyangiitis (GPA), microscopic polyangiitis, and eosinophilic GPA. This group of vasculitides can manifest at any age, affecting various organ systems, with a notable frequency of respiratory involvement in GPA and microscopic polyangiitis. Pulmonary symptoms, often similar to those of respiratory infections, frequently complicate the diagnosis. Lesions associated with alveolar hemorrhage are challenging to identify on imaging, leading to potential delays in AAV diagnosis and treatment. This case highlights the diagnostic challenges and the importance of early multidisciplinary collaboration in diagnosing AAV. Patient concerns: A middle-aged female presented with a 2-month history of recurrent cough and sputum production that did not improve with antibiotics. Initial chest computed tomography (CT) revealed multiple areas of increased density in both lungs, initially suspected as pneumonia. Diagnoses: Persistent symptoms despite antibiotic therapy, a positive anti-myeloperoxidase (MPO-IgG) antibody test, and concurrent sinusitis raised suspicion for AAV, which was confirmed through multidisciplinary consultation. Interventions: The patient was treated with prednisone and azathioprine. Outcomes: Symptomatic improvement was noted within 1 week of treatment. Follow-up chest CT at 3 months showed complete resolution of pulmonary lesions. Lessons: This case underscores the diagnostic challenges of AAV, especially when respiratory symptoms and CT findings resemble an infection. In patients with unexplained respiratory symptoms and diffuse lung changes unresponsive to antibiotics, AAV should be part of the differential. Early anti-neutrophil cytoplasmic antibody testing and multidisciplinary collaboration are crucial for timely diagnosis and treatment.