B71-23 Cavitary Lung Disease: It’s Not the Bug You Thought

Abstract Cavitary lung disease has an extensive differential. Here, we present a case of infectious cavitary lung disease caused by Corynebacterium pseudodiphtheriticum, a known commensal organism of the upper respiratory tract but has emerged as an opportunistic pathogen. A 72-year-old male with a history of stage IV cutaneous squamous cell carcinoma of the head and neck s/p radiation and immunotherapy and immunotherapy-induced enteritis treated with high-dose steroids and infliximab, presented for evaluation of dyspnea and productive cough. He was treated with antibiotics, and his steroid dose was reduced. Despite therapy, his symptoms persisted. A chest CT was completed and revealed bilateral nodular densities, the largest of which was in the right lower lobe, measuring 4.1 x 2.9 cm (Figure 1). Given his history of malignancy, he was scheduled for a biopsy, however, the scout chest CT prior to biopsy showed improvement of the nodular opacities and cavitation of the target right lower lobe opacity; thus, the biopsy was canceled. After repeating a chest CT six weeks later, new areas of cavitation and consolidation were noted. A bronchoscopy with bronchoalveolar lavage was performed. The culture returned positive for C. pseudotuberculosis. Given the rarity of this bacterium in causing disease in humans, infectious disease was consulted, and the lab re-speciated the culture, accurately identifying C. pseudodiphtheriticum. Infectious disease initiated high-dose amoxicillin with subsequent CT chest after 3 months of therapy showing improvement. C. pseudodiphtheriticum is a commensal organism of the upper respiratory tract and has previously been dismissed as a contaminant in culture. An increasing number of reports have documented its role as a causal organism in the development of tracheitis and pneumonia in the immunocompromised host, but rarely as a cause of cavitary lung disease. An observational study published in Europe identified older age and male sex, much like our patient, as potential risk factors for infection. Additionally, the initial culture was misclassified as C. pseudotuberculosis, a common cause of disease in livestock, not humans. Though this patient had risk factors for opportunistic infection including immunotherapy and high dose steroids, he did not have risk factors specific to C. pseudotuberculosis, making the initial diagnosis unlikely and stressing the importance of multidisciplinary discussion. Cavitary lung disease caused by C. pseudodiphtheriticum is rare; therefore, providers must have a high index of suspicion for disease. Appropriate identification of the causal organism is crucial for effective therapy and preventing progression of disease. This abstract is funded by: None