B73-13 When Infection Masquerades as Malignancy: Disseminated Nocardia Abscessus in an Immunocompetent Host

Abstract Nocardia are soil-dwelling, aerobic, weakly acid-fast Gram-positive bacteria causing ∼500-1,000 U.S. infections annually, ∼60% of which occur in immunocompromised hosts. Pulmonary disease is the most common presentation (involving the lung in ∼60-70% of cases). Nocardiosis can disseminate to virtually any organ (especially brain, skin, and bone), and CNS involvement carries up to 80% mortality. We present a rare case of disseminated Nocardia abscessus infection in an immunocompetent man initially misdiagnosed as lung cancer. A 63-year-old man with no significant medical history presented with 5 weeks of left-sided chest pain, hemoptysis, cough, fatigue, and weight loss. Chest CT revealed a 9 cm cavitary mass in the left upper lobe invading the mediastinum and encasing the subclavian artery, with mediastinal lymphadenopathy concerning for malignancy. Extensive infectious workup was unrevealing. Bronchoscopy with bronchoalveolar lavage and biopsy showed no evidence of malignancy or infection. He was discharged with plans for an outpatient lung biopsy.Two months later, he presented with acute right shoulder pain. Imaging showed a large lytic lesion in the right scapula, and surgical drainage grew Nocardia abscessus. Further evaluation revealed disseminated nocardiosis: L4-L5 discitis/osteomyelitis, a large right psoas abscess (∼20 cm), and multiple brain abscesses. Retrospectively, the lung lesion was an undiagnosed Nocardia infection that had spread hematogenously. The patient was treated with prolonged intravenous trimethoprim-sulfamethoxazole (TMP-SMX) plus additional antibiotics per susceptibilities. Neurosurgery recommended conservative management of the brain abscesses. After stabilization, he was discharged to continue a long course of IV antibiotics. This case highlights the diagnostic challenge of nocardiosis in an immunocompetent host. Nocardiosis is classically an opportunistic infection in immunocompromised patients. However, immunocompetent individuals can develop severe nocardiosis after environmental exposure. In our patient, the pulmonary infection was mistaken for cancer, illustrating how Nocardia’s diverse radiographic manifestations can mimic malignancy or tuberculosis. Missed diagnosis is dangerous as disseminated nocardiosis requires prolonged multidrug therapy and carries high mortality, especially with CNS involvement. Optimal management includes a high index of suspicion, brain imaging to screen for CNS involvement, and alerting the lab to prolong cultures for Nocardia isolation. High-dose TMP-SMX is the backbone of therapy, often combined with a carbapenem for severe or CNS disease. This extensive multi-organ infection in an immunocompetent host underscores the need to consider nocardiosis even without classic risk factors to ensure timely diagnosis and prevent life-threatening dissemination. This abstract is funded by: none