Abstract Introduction Diffuse alveolar hemorrhage (DAH) is a life-threatening complication caused by the destruction of small pulmonary vessels. Unilateral presentations are rare and may delay diagnosis. We present a case of unilateral DAH due to p-ANCA-associated vasculitis in a 60-year-old woman without significant renal involvement. Case Presentation A 60-year-old woman presented with hemoptysis, dyspnea, hypoxia (SpO2 87%), and profound anemia (hemoglobin 5.6 g/dL). Her medical history was significant for CAD, hypertension, COPD, and Raynaud’s phenomenon. Serum creatinine was elevated, while urinalysis revealed only hyaline casts (no dysmorphic red cells or proteinuria), suggesting prerenal azotemia secondary to hypovolemia. Chest CT pulmonary angiography excluded pulmonary embolism but revealed diffuse ground-glass opacities in the right middle and upper lobes with associated right-sided hilar lymphadenopathy. The unilateral ground-glass pattern in a vasculitis DAH context remains highly unusual. Bronchoscopy confirmed alveolar hemorrhage with hemosiderin-laden macrophages. Serologic testing was notable for positive myeloperoxidase-ANCA (p-ANCA) and negative anti-glomerular basement membrane (anti-GBM) antibodies, cytoplasmic ANCA (c-ANCA), and ANA. Infectious work-up was also unremarkable. Given the absence of glomerular hematuria or active urinary sediment, renal involvement was insignificant. The patient was treated with high-dose intravenous methylprednisolone (1 g daily for three days), followed by oral prednisone (60 mg daily) with gradual tapering. Inhaled tranexamic acid was administered as adjunctive therapy, and multiple red-cell transfusions were administered. Her clinical status gradually improved with resolution of hemoptysis, hypoxia, and stabilization of hemoglobin. She was transitioned to maintenance therapy with mycophenolate mofetil and continues to do well. Discussion This case highlights several atypical features: (1) small-vessel vasculitis (microscopic polyangiitis) presenting with unilateral rather than bilateral DAH, (2) absence of overt renal involvement despite p-ANCA positivity, and (3) profound anemia without an identifiable extrapulmonary bleeding source. Standard DAH management with high-dose corticosteroids was effective. Early bronchoscopy with demonstration of hemosiderin-laden macrophages / progressively bloodier aliquots remains diagnostic, and prompt immunosuppression is essential to reduce morbidity and mortality. This case adds to the limited literature on unilateral vasculitis-mediated DAH and emphasizes the importance of considering vasculitis in the differential diagnosis of unilateral diffuse ground-glass opacities. Conclusion Unilateral diffuse alveolar hemorrhage in the setting of p-ANCA positive microscopic polyangiitis is rare but clinically significant. Early recognition and timely initiation of immunosuppressive therapy are critical for favorable outcomes. This abstract is funded by: None
Bashir et al. (Fri,) studied this question.