Abstract:Objective To analyze the clinical characteristics of patients with pulmonary nocardiosis (PN). Methods Clinical data of patients with PN diagnosed by metagenomic next-generation sequencing (mNGS) in a hospital from September 2019 to December 2022 were retrospectively analyzed, and patients' clinical characteristics were analyzed and summarized. Results Among the 15 patients with PN, 14 were males and 1 was female, aged 36-83 years old. 14 patients had underlying diseases, 3 of whom used immunosuppressants or glucocorticoids chronically. 11 cases were simple PN, and two sites were simutaneously invaded in 4 cases, 2 of whom spread to the blood, 1 case to the liver, and 1 case to the central nervous system on the basis of PN. Cough and expectoration were the most common symptoms (73.33%). The percentage of neutrophils, C-reactive protein and procalcitonin increased, CD4+T cell count and albumin decreased. Chest imaging showed that unilateral lung lesions were more common, mostly occurred in the right lung in the form of cavities, patchy shadows, bronchiectasis, nodular shadow, tree-in-bud sign, and consolidation shadow. Among the 15 patients, only 1 was treated with sulfonamides, 12 were treated with sulfonamides combined with other antimicrobial agents, and 2 were treated with other antimicrobial combination. 14 patients improved after treatment, and 1 patient died. Conclusion PN often occurs in patients with underlying diseases and compromised immunity. With atypical clinical characteristics, it is prone to be misdiagnosed. mNGS can diagnose promptly and accurately. Early, adequate, and full-course sulfonamide-based antimicrobial combination treatment generally results in good prognosis.