Abstract Diffuse alveolar hemorrhage (DAH) is a condition characterized by widespread bleeding into the alveoli through disruption of the alveolar-capillary membrane. It usually presents with nonspecific symptoms such as cough, hemoptysis, and dyspnea. DAH is frequently associated with small-vessel vasculitides, such as microscopic polyangiitis (MPA). MPA is a systemic, necrotizing form of small-vessel vasculitis that causes endothelial inflammation and injury, particularly affecting the kidneys and respiratory tract. In MPA, decreased immune tolerance of myeloperoxidase (MPO) prompts the formation of myeloperoxidase-antineutrophil cytoplasmic antibodies (MPO-ANCA). In the setting of DAH, MPA leads to pulmonary capillaritis, necrosis of the alveolar septa causing structural degradation and hemorrhage. 25-year-old male presents to the ED with a 1-week history of hemoptysis and hematuria. Upon evaluation in the ED, patient was noted to be tachypneic and tachycardic requiring BiPAP for respiratory support. Initial workup was significant for AKI and acute anemia. Chest X-ray showed diffuse interstitial and alveolar opacities, initially thought to be infectious vs edematous in nature. Heparin was also briefly started for possible pulmonary embolism but was quickly discontinued following worsening anemia and hemoptysis. Bronchoscopy was performed in setting of worsening respiratory distress with bronchoalveolar lavage with grossly pure blood. Autoimmune panel was positive for rheumatoid factor and ANA. Given these results and presentation of hemoptysis with hematuria, nephrology was consulted for further evaluation of possible systemic vasculitis. Renal biopsy was performed which revealed crescentic glomerulonephritis with positive MPO antibodies concerning for a pauci-immune vasculitis consistent with microscopic polyangiitis. After establishing vasculitis as the underlying etiology, the patient was subsequently treated with high-dose methylprednisolone and rituximab infusions. Repeat imaging performed one month later demonstrated complete resolution of bilateral infiltrates.Diffuse alveolar hemorrhage (DAH) has a broad differential, including autoimmune, infectious, and drug-induced causes. Bronchoscopic or histological evaluation may be required to establish the underlying diagnosis. In cases of microscopic polyangiitis, DAH is often due to early pulmonary capillaritis. Initial chest imaging may mimic pneumonia, which can delay diagnosis. While uncommon, DAH due to vasculitis should remain on the differential in patients with hemoptysis and diffuse infiltrates, particularly when accompanied by renal dysfunction. First-line therapy for DAH due to MPA includes high-dose corticosteroids combined with immunosuppressive agents such as rituximab or cyclophosphamide. Prognosis of DAH varies widely and is closely tied to the underlying cause. In ANCA-associated vasculitis, 5-year all-cause mortality is estimated to approach 25 percent. This abstract is funded by: None
Urvina et al. (Fri,) studied this question.