Nocardia infection Presenting as a mediastinal mass in a ceramic worker diagnosed by EBUS-TBNA

W. Wu^a (Dr), X. Su^a (Mrs), C. Lin^a (Dr), Z. Zhuang^b (Mr), Z. Yixiang^a (Dr), X. Lin^a (Dr), H. Jiaming^a (Mrs), Z. Zhu^a (Dr), Z. Huaping*^a (Dr)

^a The Second Affiliated Hospital of Fujian Medical University, Quanzhou, CHINA ; ^b Quanzhou Jinjiang Anhai Hospital, Quanzhou, CHINA

* fmuzhp@126.com

Background: Nocardia is ubiquitous soil saprophytes that are transmitted by either airborne or direct cutaneous inoculation route. Nocardia species more frequently cause invasive infections in immunocompromised patients but might be observed in immunocompetent patients. Case presentation: We report a rare case of Nocardia infection presenting as a large mediastinal mass in an immunocompetent ceramic worker. A 54-year-old man with no previous history of immune dysfunction, a ceramic worker by profession, was referred and admitted to our hospital because of a persistent fever for 19 days. Chest CT showed multiple nodules on the right lung and a large middle mediastinal mass. Anti-infective treatment was ineffective. To identify the etiology, we performed Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) and obtained purulent exudates which were further identified as Nocardia species by weakly acid-fast and metagenomic next-generation sequencing (mNGS). He was subsequently treated with intravenous imipenem/amikacin, switched to intravenous imipenem and oral trimethoprim/sulfamethoxazole, and the clinical symptoms were significantly improved. After this, the patient improved and he was discharged. He continued on oral trimethoprim-sulfamethoxazole for 6 months. During the last year and a half of follow-up, the patient recovered well, with no complications, and CT findings of the mediastinal mass improved significantly. Conclusions: Patients with subacute to chronic respiratory symptoms, elevated inflammatory markers, mediastinal masses, a history of soil-related occupational exposure, and absence of common respiratory pathogens under evaluation are high indicators of suspected Nocardia infection. An invasive approach may be necessary to obtain tissue diagnosis to direct treatment in these cases. EBUS-TBNA is a useful and safe technique for the diagnosis of mediastinal infectious lymphadenopathy of unknown origin. Once the diagnosis is established, prompt antibiotic therapy should be performed, and these appropriate medications can lead to significant radiological improvement.

Disclosure of funding source(s):

This work was sponsored by the Fujian Provincial Natural Science Foundation (2021J01258) and the Talent Training Project of the Provincial Respiratory Medical Center (HXZX202204).