Background  Nocardia is an opportunistic pathogen with lung as the most frequently involved organ. However, the clinical symptoms and imaging features of pulmonary nocardiosis are not specific, so it is easy to be misdiagnosed or miss diagnosed.

  Objective  To investigate the clinical features, imaging manifestations, treatment and prognosis of pulmonary nocardiosis.

  Methods  Clinical data about patients diagnosed with pulmonary nocardiosis in Shengli Oilfield Hospital from January 2017 to December 2021 were collected and analyzed retrospectively.

  Results  There were 16 patients with pulmonary nocardiosis, including 6 males and 10 females, aged 43-87 years old, 6 cases were combined with autoimmune diseases receiving long-term oral glucocorticoid, and 10 cases with chronic structural lung diseases; Among 16 patients, cough and sputum was found in 15 cases (93.7%), fever in 12 cases (75.0%), and dyspnea in 12 cases (75.0%); Nodule or mass (14/16), with cavities (8/16), multiple plaque shadow (10/16), consolidation (6/16) were the major imaging manifestations, and others including pleural thickening, mediastinal lymph node enlargement, bronchiectasis, pleural effusion were also seen in some patients. White blood cell count, neutrophil ratio and C reaction protein were elevated in most of the patients. Normal or mildly elevated calcitoninogen (≤0.5 ng/mL) were seen in 10 cases (62.5%), while significant elevated calcitoninogen (＞0.5 ng/mL) in 6 cases (37.5%). The diagnosis of nocardia infection was made by sputum culture and alveolar lavage fluid culture, and its treatment was based on sulfonamide therapy with good prognosis achieved in most cases.

  Conclusion  For immunosuppressed hosts or patients with chronic structural lung diseases, when empirical anti-infection treatment fails, we should consider the possibility of pulmonary nocardiosis. Early access to pathogenic results and timely anti-infection treatment are of great significance to improve prognosis.