B35-31 Evolving Granulomatous Lung Lesion Revealing Granulomatosis With Polyangiitis

Abstract Introduction Granulomatosis with polyangiitis (GPA) is a rare necrotizing small-vessel vasculitis that can initially present with isolated pulmonary lesions, often mimicking malignancy or infection. Diagnosis is challenging when early biopsies are inconclusive and systemic features evolve gradually. Case Description A 59-year-old African American woman presented with a persistent cough and right-sided chest discomfort. Chest CT revealed a 5.5 × 3.8 × 4.7 cm posterior right lower-lobe juxtapleural mass (Figure 1), along with multiple smaller nodules scattered throughout both lungs. Bronchoscopic and endobronchial ultrasound-guided biopsies demonstrated focal necrosis and granulation tissue, without evidence of malignancy or infection. PET-CT showed hypermetabolic activity, raising concern for both inflammatory and neoplastic etiologies. She was started on corticosteroids, which led to rapid symptomatic improvement and partial regression of the pulmonary lesions. Laboratory testing showed low-titer cytoplasmic ANCA and anti-proteinase 3 (PR3) positivity, suggesting limited GPA. Methotrexate was added to facilitate steroid tapering.Over the following months, the patient developed proteinuria, hematuria, and rising serum creatinine. Renal biopsy revealed crescentic pauci-immune glomerulonephritis, confirming systemic GPA. She received induction therapy with intravenous cyclophosphamide and high-dose corticosteroids, resulting in stabilization of renal function and further radiologic improvement in her lung lesions. Figure 1. High-resolution CT scan was notable for bilateral pulmonary nodules, some of which demonstrate cavitary changes with adjacent ground-glass opacification. Discussion This case highlights the diagnostic challenge of GPA when presenting as a solitary or dominant pulmonary mass with initially nondiagnostic biopsies and steroid-responsive lesions. The progression from localized pulmonary disease to systemic vasculitis underscores the need for close follow-up with serial imaging, laboratory monitoring, and multidisciplinary evaluation. GPA should remain in the differential diagnosis for patients with recurrent or cavitary pulmonary nodules, especially when ANCA titers rise or renal involvement develops. Early recognition and prompt initiation of immunosuppressive therapy are critical to prevent irreversible organ damage and improve outcomes. This abstract is funded by: None