Clinical features of pulmonary nocardiosis: a descriptive research study.

INTRODUCTION: Pulmonary nocardiosis lacks specific symptoms and characteristic test findings, making diagnosis and treatment challenging. Therefore, to clarify its clinical features, we analyzed 21 cases diagnosed as pulmonary nocardiosis at our institution. METHODS: We conducted a retrospective review of cases in which Nocardia species were isolated from respiratory specimens at Saitama Red Cross Hospital between January 2017 and May 2024. RESULTS: The cohort included 14 females and 7 males, with a mean age of 71.8 years. Underlying lung diseases were present in 14 cases (66.7%), with pulmonary nontuberculous mycobacterial (NTM) disease being the most common (8 cases). Mixed infections with other bacteria were observed in 10 cases (47.6%) at the time of pulmonary nocardiosis diagnosis, including 4 cases involving NTM. Additionally, during follow-up after diagnosis, 4 patients (19.0%) developed mixed infections with Pseudomonas aeruginosa. The prognosis of pulmonary nocardiosis itself was favorable. CONCLUSION: Given that many patients have underlying lung diseases and that mixed infections (particularly with NTM and P. aeruginosa) are frequently observed both at diagnosis and during follow-up, it is crucial to always consider the possibility of pulmonary nocardiosis when symptoms or imaging findings worsen.