C41-10 When Aspiration Isn’t Simple: Anca-Associated Vasculitis Presenting as Pulmonary-Renal Syndrome Following Upper Gastrointestinal Bleeding

Abstract Introduction Aspiration pneumonia is a frequent cause of hypoxemia in elderly patients following upper gastrointestinal bleeding. However, when respiratory failure and renal dysfunction occur simultaneously, pulmonary-renal syndromes such as antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis should be considered. We report an elderly patient initially presumed to have aspiration-related respiratory failure after hematemesis, later diagnosed with ANCA-associated vasculitis presenting as pulmonary-renal syndrome. Case Report An 87-year-old man with atrial fibrillation (status post Watchman device), hypertension, and diabetes mellitus presented with hematemesis and melena. Two weeks earlier, he had been hospitalized for rib fractures and a right pleural effusion, empirically treated for aspiration pneumonia. On presentation, hemoglobin was 6.7 g/dL and serum creatinine 3.6 mg/dL (baseline 0.8-1.0 mg/dL).Esophagogastroduodenoscopy revealed an oozing esophageal ulcer and gastric angiodysplasias treated with argon plasma coagulation. Following the procedure, his oxygen requirement escalated from 2 L/min nasal cannula to 15 L via nonrebreather mask, accompanied by new-onset hemoptysis. Chest computed tomography showed diffuse left lung ground-glass opacities concerning for alveolar hemorrhage. Despite empiric antibiotics and diuretics, he developed acute hypoxemic respiratory failure requiring intubation. Serum testing was positive for cytoplasmic ANCA (1:80) and elevated proteinase-3 (PR3 8.0 U/mL) with normal complement levels. Renal function worsened rapidly (creatinine 3.6 → 9.2 mg/dL over five days) with new microscopic hematuria and proteinuria (urine protein/creatinine ratio 420 mg/g). Renal biopsy revealed necrotizing and crescentic pauci-immune glomerulonephritis, confirming ANCA-associated vasculitis. High-dose intravenous methylprednisolone (500 mg daily × 3 days) followed by oral prednisone 40 mg daily and rituximab resulted in rapid improvement: creatinine decreased to 3.4 mg/dL within three days, hemoptysis resolved, and he was extubated to nasal cannula. He was discharged to a rehabilitation facility on oral prednisone with scheduled rituximab maintenance and outpatient dialysis. Discussion This case highlights how diffuse alveolar hemorrhage from ANCA-associated vasculitis can masquerade as aspiration pneumonitis, particularly after gastrointestinal bleeding. In elderly patients, aspiration is often presumed when hypoxemia follows hematemesis, but persistence of respiratory failure with concurrent renal dysfunction should raise concern for vasculitic pulmonary-renal syndromes. Early recognition and initiation of corticosteroids and rituximab are crucial for reversing multi-organ dysfunction. Clinicians must maintain diagnostic flexibility when common explanations fail to account for a patient’s clinical trajectory. This abstract is funded by: None