Abstract Introduction ANCA-associated vasculitides (AAV) are small-vessel necrotizing vasculitides characterized by autoantibodies against neutrophil cytoplasmic components—most commonly proteinase-3 (PR3) and myeloperoxidase (MPO). The major subtypes—granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA)—frequently involve the lungs, though manifestations are highly variable. We present four cases highlighting distinct pulmonary presentations of AAV (Figure 1): (1) organizing pneumonia (OP) in interstitial lung disease (ILD) (A), (2) diffuse alveolar hemorrhage (DAH) (B), (3) pulmonary mass (C), and (4) pulmonary nodules (D). Case Presentations Case 1: A 46-year-old woman with end-stage renal disease presented with recurrent hemoptysis and dyspnea refractory to antibiotics. HRCT showed bilateral ground-glass opacities; biopsy revealed an OP pattern with fibroinflammatory scarring. Serologies were positive for p-ANCA/MPO, supporting MPA. She improved with prednisone and rituximab. Case 2: A 26-year-old man with chronic sinusitis presented with necrotic digital lesions, scrotal pain, dyspnea, and hemoptysis. CTA showed diffuse bilateral peribronchovascular ground-glass opacities with subpleural sparing, consistent with DAH. Serologies positive for c-ANCA/PR3 confirmed GPA. Despite steroids and rituximab, he relapsed and required plasmapheresis, cyclophosphamide, and prolonged taper. Case 3: A 46-year-old woman with prior herpes zoster ophthalmicus presented with dyspnea and chest pressure. HRCT revealed a right middle lobe mass-like opacity with pulmonary nodules. Serologies were positive for c-ANCA/PR3, and biopsy confirmed GPA. She improved with prednisone and rituximab, later switched to mycophenolate for intolerance, with resolution of the mass. Case 4: A 23-year-old woman with asthma and chronic sinusitis presented with dyspnea and cough. CT showed pulmonary nodules; cryobiopsy revealed necrotizing granulomas with acute pneumonitis and alveolar hemorrhage. p-ANCA/MPO positivity (negative PR3) supported MPA. She improved with pulse steroids and rituximab. Discussion Pulmonary involvement in AAV is remarkably heterogeneous. While ILD is increasingly recognized in MPA, the OP pattern remains rare yet highly responsive when compared to other AAV-ILD patterns, underscoring the importance of early recognition. Case 4 expands the phenotypic spectrum of MPA, illustrating that cavitary nodules can occur despite its usual ILD or diffuse alveolar damage pattern. Isolated mediastinal masses are exceedingly rare in GPA (2% of cases), posing diagnostic challenges in distinguishing pseudotumor from malignancy. Life-threatening complications of GPA, such as DAH, as seen in Case 2, remain a major cause of morbidity and mortality, requiring prompt, individualized escalation of therapy. Collectively, these cases highlight the diagnostic complexity and therapeutic challenges of pulmonary AAV, as well as the need for vigilance when presentations deviate from classic patterns. This abstract is funded by: None
Somaratna et al. (Fri,) studied this question.