Diagnosis and treatment of a patient with mediastinal infection caused by Emergomyces orientalis and Mycobacterium fortuitum.

BACKGROUND

Emergomycosis, an emerging dimorphic fungal infection caused by Emergomyces species, primarily affects immunocompromised individuals. Emergomyces orientalis has been reported in China, including rare cases in immunocompetent individuals. Diagnosis remains challenging due to the lack of typical clinical manifestations and radiological features. Co-infection with other pathogens further complicates management, with no prior global reports of concurrent E. orientalis and non-tuberculous mycobacterial (NTM) infections.

CASE PRESENTATION: A 21-year-old immunocompetent woman with occupational exposure to soil presented with cough, fever, and a mediastinal mass on chest CT. The initial biopsy specimens revealed granulomatous inflammation and yeast-like fungi. Metagenomic next-generation sequencing (mNGS) of endobronchial ultrasound (EBUS)-guided specimens confirmed E. orientalis (40 reads). Liposomal amphotericin B induction therapy initially relieved the symptoms. However, recurrence prompted repeat mNGS, which revealed elevated Mycobacterium fortuitum loads (791 reads). Combined with the patient's history of soil exposure, a diagnosis of mediastinal E. orientalis with M. fortuitum co-infection was established based on the clinical presentation, the chest CT findings, histopathological observations of yeast-like fungi, the mNGS results, and the therapeutic response. Following confirmation of the co-infection, tailored adjustments to the antimicrobial regimen led to successful clinical management.

CONCLUSION

To the best of our knowledge, this is the first study in which E. orientalis and M. fortuitum were documented to coexist in the mediastinum. The dual pathogens were identified through a combination of EBUS-guided biopsy and mNGS. Accurate pathogen identification followed by tailored, pathogen-directed therapy is essential for the effective management of an E. orientalis and M. fortuitum mixed infection.