Probable Exophiala oligosperma-associated pulmonary granulomatous inflammation: a case report

Differentiating the underlying etiologies of pulmonary granulomatous lesions is of paramount clinical importance. Reliable identification of infectious pathogens relying solely on histopathological sections frequently proves difficult and lacks adequate sensitivity. Comprehensive integration of clinical data, imaging findings, pathological evidence, and pathogen testing results is therefore indispensable to achieve a final clinical diagnosis. A 45-year-old man presented to the clinic with chest tightness and shortness of breath on exertion for three weeks. After the onset of dyspnea, chest computed tomography (CT) at a local hospital revealed diffuse pulmonary nodules. Targeted Next-Generation Sequencing (tNGS) of bronchoalveolar lavage fluid (BALF) detected Streptococcus pneumoniae. However, empirical antibacterial therapy yielded no clinical efficacy. Follow-up chest CT showed continuous progression of pulmonary lesions. The patient was subsequently hospitalized. Transbronchial lung cryobiopsy revealed pulmonary granulomatous inflammation, while special pathological staining for pathogens was negative. Notably, metagenomic Next-Generation Sequencing (mNGS) of BALF identified 88 reads of Exophiala oligosperma , corresponding to a reads-per-ten-million (RPTM) of 34. Integrating clinical, imaging, pathological and etiological evidence, the case was ultimately suspected to be probable pulmonary Exophiala oligosperma infection. The patient received nine-week antifungal therapy. At the three-month follow-up after drug discontinuation, chest CT demonstrated complete resolution of the pulmonary lesions, indicating favorable therapeutic outcomes. This study reports an extremely rare case of pulmonary granulomatous inflammation associated with Exophiala oligosperma . This case provides valuable clinical evidence for the recognition and differential diagnosis of atypical fungal pulmonary diseases.