C42-29 A Clinical Dilemma: Differentiating Drug-Induced Pneumonitis From Opportunistic Infection in a Critically Ill Patient

Abstract Introduction Acute respiratory distress syndrome (ARDS) is a severe condition characterized by impaired pulmonary gas exchange, leading to hypoxemia and is caused by multiple causes. Daptomycin, a widely used antibiotic, has been associated with lung injury particularly daptomycin-induced eosinophilic pneumonia (DEP). The cornerstone of treatment for DEP is the immediate discontinuation of daptomycin, along with supportive care. Another rare cause of ARDS is Pneumocystis jirovecii infection, which primarily affects immunocompromised individuals. Although most patients respond well to appropriate therapy, a subset may experience worsening respiratory status despite treatment. Case A 65-year-old male with a history of organizing pneumonia, COPD, cirrhosis, hypothyroidism presented with leukocytosis and elevated CK following a 4-week course of daptomycin for right hip osteomyelitis. Initial chest imaging showed extensive bilateral ground-glass opacities with patchy reticulonodular changes, raising concern for pneumonitis or pneumonia. CT of the pelvis revealed bilateral femoral head avascular necrosis, while blood cultures were negative. Orthopedic consultation advised no acute surgical intervention, and oral antibiotics were continued for osteomyelitis. Due to concern for daptomycin-induced eosinophilic pneumonia, daptomycin was discontinued, and therapy was transitioned to vancomycin, levofloxacin, and metronidazole. Bronchoscopy with BAL revealed lymphocytic alveolitis without eosinophils, ruling out daptomycin-induced pneumonia. However, the Pneumocystis Jirovecii DFA test was positive. The patient was started on trimethoprim-sulfamethoxazole and corticosteroids. Despite treatment, respiratory status worsened, requiring escalation from high-flow nasal cannula to BiPAP, and ultimately invasive mechanical ventilation. The P/F ratio was 100 and repeat CT imaging showed worsening infiltrates consistent with ARDS. Management included proning, which led to partial improvement. An extensive secondary infectious workup—including Karius testing, respiratory viral panel (positive for Parainfluenza 2), urine histoplasma and Blastomyces antigens, cryptococcal antigen, beta-D-glucan, and galactomannan were negative. Multiple ventilator weaning attempts were unsuccessful. The patient is now planning for tracheostomy and transfer to a long-term acute care facility following medical optimization. Discussion This case highlights the complexity of managing severe PJP in a patient with multiple comorbidities and prior immunosuppressive therapy. It is imperative to be able to recognize this disease process and provide aggressive supportive care while coordinating multidisciplinary management in critically ill patients, especially given the reported mortality rate of up to 60% among those requiring intensive care or mechanical ventilation. It also emphasizes the need to rule out drug-induced lung injury, particularly with daptomycin. This abstract is funded by: None