B73-20 Isolated Hyperbilirubinemia in Legionella Pneumonia

Background Legionella pneumophila pneumonia is an atypical yet relatively common diagnosis that can lead to severe complications. Early recognition is critical, as timely initiation of targeted therapy can significantly improve outcomes. This is a case of Legionella pneumonia in a patient whose initial laboratory findings demonstrated marked isolated hyperbilirubinemia—an uncommon but potentially diagnostic clue. Case Presentation A 42-year-old female with a history of HIV, nonadherent to her Biktarvy therapy, was admitted for altered mental status and encephalopathy. Her family found her lying on the ground, covered in feces, and acutely confused.On presentation to the emergency department, she appeared toxic and in acute distress. Chest radiography revealed a right lower lobe pneumonia. Laboratory findings were significant for a total bilirubin of 11.9 mg/dL, lactic acid of 6.4 mmol/L, and a positive acetaminophen level.She was admitted to the ICU for management of aspiration pneumonia, hepatic encephalopathy, and possible acetaminophen overdose, requiring intubation that night for airway protection. A hepatitis panel and right upper quadrant ultrasound were negative for intrinsic liver disease.Infectious Disease consultation raised concern for Legionella infection as the source of her hyperbilirubinemia. Subsequent testing confirmed Legionella pneumophila infection. With appropriate management and supportive care, the patient passed spontaneous awakening and breathing trials, was successfully extubated, and transferred to the general medical floor. Discussion Legionella pneumophila accounts for approximately 2–15% of all community-acquired pneumonias requiring hospitalization (Chahin & Opal, 2017). Risk factors include advanced age, smoking, chronic lung disease, and immunocompromised states such as HIV infection. Because the presentation can be variable and overlap with other causes of pneumonia, Legionella infections are frequently underdiagnosed.The disease can progress rapidly, leading to respiratory failure, septic shock, and the need for mechanical ventilation. Recognizing atypical laboratory findings—such as hyponatremia, elevated liver enzymes, and in this case, isolated hyperbilirubinemia—may assist in early diagnosis. Our patient’s marked bilirubin elevation in the absence of other hepatic pathology pointed toward Legionella as a key etiologic consideration. Conclusion Legionella pneumophila pneumonia remains an important and potentially severe cause of community-acquired pneumonia. This case highlights that isolated hyperbilirubinemia, in the appropriate clinical context, may serve as an early diagnostic clue to Legionella infection—prompting earlier targeted therapy and preventing further complications. Reference: Chahin A, Opal SM. Severe Pneumonia Caused by Legionella pneumophila: Differential Diagnosis and Therapeutic Considerations. Infect Dis Clin North Am. 2017;31(1):111–121. doi:10.1016/j.idc.2016.10.009. PMID: 28159171; PMCID: PMC7135102. This abstract is funded by: None