A49-16 Fulminant Course of Legionella Pneumonia in an Immunocompromised Host

Abstract Introduction Although Legionella pneumophila accounts for only ∼2% of community-acquired pneumonia cases, it represents a disproportionately frequent pathogen among patients with severe pneumonia requiring ICU care, comprising nearly 10% of isolates. We report a fulminant case of Legionnaires’ disease in an HIV-infected patient who developed the classic triad of pneumonia, rhabdomyolysis, and acute kidney injury, with rapid progression to death despite aggressive supportive care. Case Presentation A 44-year-old African American man with a history of HIV infection on cabotegravir/rilpivirine was brought to the Emergency Department after an unwitnessed fall and altered mental status. He was initially found to be hypoglycemic and gradually regained consciousness following dextrose administration. Review of systems was notable only for extreme thirst. He resided in an assisted-living facility with no recent travel or known outbreak exposure.On arrival, his blood pressure was 102/63 mmHg, heart rate 123 bpm, respiratory rate 24 breaths/min, and temperature 98.6 °F. Oxygen saturation was 98% on 2 L/min nasal cannula. He appeared hypovolemic, and auscultation revealed crackles localized to the right lower lung field.Initial investigations demonstrated high-anion gap metabolic acidosis (pH 7.14, bicarbonate 8 mmol/L, lactate 7.6 mmol/L). Additional findings included hyponatremia (Na 127 mEq/L), azotemia (BUN 90 mg/dL, creatinine 8.0 mg/dL), and elevated creatine kinase (17,039 U/L). Liver function tests showed AST 1,254 U/L, ALT 137 U/L, and elevated total bilirubin with normal alkaline phosphatase. Urinary antigen testing was positive for Legionella. His absolute CD4 count was later found to be 101 cells/µL.Chest radiography revealed a right middle-to-lower lobe consolidation. The patient was started on intravenous bicarbonate infusion and broad-spectrum antibiotics with piperacillin-tazobactam, vancomycin, and azithromycin before transfer to the intensive care unit.Within ten hours of admission, his acute hypoxemic respiratory failure worsened and required endotracheal intubation. He also developed refractory septic shock necessitating quadruple vasopressors. A trial of methylene blue was administered without improvement. Despite maximal supportive measures, cardiac arrest ensued twenty hours after admission and the patient could not be resuscitated. Discussion Legionella is typically transmitted through inhalation of contaminated aerosolized water, although the source could not be identified in this case. The triad of pneumonia, rhabdomyolysis, and AKI, though rare, carries mortality approaching 50%. Studies show that HIV patients with CD4 200 cells/µL have outcomes comparable to non-HIV patients, indicating immune status and viral control modulate disease severity. Conclusions Legionella infection in immunocompromised hosts can progress catastrophically despite timely antibiotics. The presence of Legionella triad is associated with high mortality. This abstract is funded by: None