Abstract Introduction Diffuse alveolar hemorrhage (DAH) is a life-threatening pulmonary syndrome that may result from infection, drug toxicity, or immune-mediated capillaritis. Vasculitic DAH is classically associated with ANCA-positive small-vessel diseases, yet pulmonary involvement from leukocytoclastic vasculitis (LCV) is exceedingly rare. We present a diagnostically challenging case of DAH in a patient with multisystem LCV complicated by Pneumocystis jirovecii pneumonia (PJP), highlighting the intersection of infection and autoimmune injury in an immunosuppressed host. Case Presentation A 66-year-old man with biopsy-proven cutaneous LCV and severe ocular inflammatory disease consistent with peripheral ulcerative keratitis presented with acute hypoxemic respiratory failure following several months of prednisone 60 mg daily and methotrexate. He had not received PJP prophylaxis. On admission, he required 6 L/min oxygen; CT chest showed diffuse bilateral ground-glass opacities with small cystic changes. Laboratory results included LDH 564 U/L and β-D-glucan 500 pg/mL. Despite empiric antibiotics and later high-dose TMP-SMX, his oxygen requirements escalated to 40 L/min at 100% FiO2 by hospital day 7.Bronchoscopy revealed progressively bloodier lavage aliquots confirming DAH. Cytology demonstrated rare GMS-positive Pneumocystis organisms without other pathogens. Serologic testing was negative for ANCA, anti-GBM, ANA, and cryoglobulins. Renal biopsy later showed focal segmental glomerulosclerosis without immune deposits, suggesting prior immune injury. His broader history of steroid-responsive purpuric rash, chronic sinusitis requiring surgery, and ocular cicatricial disease supported a diagnosis of systemic but ANCA-negative LCV. Discussion Although LCV most often manifests as a cutaneous small-vessel vasculitis, pulmonary involvement and DAH are exceptionally uncommon, with fewer than 20 cases reported worldwide¹. Proposed mechanisms include immune-complex-mediated capillaritis and secondary endothelial injury triggered by infection or drugs². P. jirovecii infection itself can provoke alveolar hemorrhage through diffuse alveolar damage and inflammatory capillaritis³. In this patient, DAH likely arose from synergistic injury—immune-mediated vascular inflammation potentiated by opportunistic infection during high-dose steroid exposure. This case emphasizes that LCV, though typically skin-limited, may evolve into a systemic vasculitic process involving the lungs and kidneys. The absence of ANCA or immune deposits should not exclude vasculitic DAH, particularly in patients with corroborating cutaneous or ocular findings. Clinicians must also balance immunosuppression against infection risk and maintain vigilance for overlapping etiologies4.ConclusionDAH in the setting of LCV represents a rare but severe systemic progression of a classically cutaneous vasculitis. This case illustrates how chronic immunosuppression can blur the boundaries between infection and inflammation, underscoring the need for early diagnostic bronchoscopy, infection prophylaxis, and interdisciplinary management. This abstract is funded by: None
T Narra (Fri,) studied this question.