Cavitary Pulmonary Tuberculosis with Orientia tsutsugamushi Coinfection in a Non-Endemic Region: A Case Report

Yuanjiang Zheng¹Jiangyan Hou²Li Yang²Youjun Jiang¹Shanyu Wang²Jianglin Yu²Xianwei Ye^1*

• ¹Guizhou Provincial People's Hospital, Guiyang, China
• ²Zunyi Medical University, Zunyi, China

Introduction: Coinfection of pulmonary tuberculosis and scrub typhus caused by Orientia tsutsugamushi is exceptionally rare. Overlapping clinical and radiologic features, together with the frequent absence of clear epidemiologic clues, complicate timely diagnosis. Case presentation: A 57-year-old man residing in a non-endemic region presented with a left-sided cavitary lung lesion on imaging. Computed tomography (CT)-guided percutaneous lung biopsy, acid-fast bacillus staining, and Mycobacterium tuberculosis DNA PCR established the diagnosis of active cavitary pulmonary tuberculosis. Despite initiation of a standard first-line anti-tuberculosis regimen, high-grade fever persisted. Metagenomic next-generation sequencing (mNGS) of bronchoalveolar lavage fluid (BALF) detected O. tsutsugamushi, which was subsequently confirmed by a positive IgM indirect immunofluorescence assay (IFA). Doxycycline was added, leading to defervescence within 48 hours and marked symptomatic improvement. On follow-up, chest CT demonstrated lesion absorption and cavity shrinkage, while new fibrotic changes emerged. The patient was started on maintenance pirfenidone and prescribed home oxygen therapy. Conclusions: In patients with pulmonary tuberculosis who exhibit persistent fever or suboptimal response despite appropriate therapy—and after excluding drug resistance—scrub typhus should be included in the differential diagnosis, even in non-endemic settings without a typical exposure history. Longitudinal imaging in this case also shows that irreversible structural remodeling may occur despite microbiologic control, underscoring the need to pair prompt pathogen-directed therapy with ongoing monitoring and early strategies to preserve lung function.