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© Author(s) (or their employer(s)) 2023. No commercial reuse. See rights and permissions. Published by BMJ. A 38yearold woman presented with a 1month history of progressive cough and phlegm. She was an office worker. She denied the presence of comorbidities including diabetes, renal disease, malignancy and acquired immune deficiency syndrome. She underwent chest CT scan (figure 1A) 2 weeks before admission, having been taking moxifloxacin treatment for 12 days without improvement in symptoms. A repeat CT scan at admission showed significant progression of the lung lesions compared with previous imaging (figure 1B). Sputum culture was negative. Laboratory investigations revealed NK cells, CD4+, CD8+ lymphocytes and the CD4+/CD8+ lymphocytes ratio, serum interferon-γ, TNF-α, immunoglobulins (IgG, IgA and IgM), and complement components 3 and 4 detections were all in the normal range. A bronchoscopy showed mucoid impactions completely obstructed the anterior basal segment of the right lower lobe (figure 1C). Radial endobronchial ultrasound (EBUS) was used to detect the lesion in the bronchial lumen (figure 1D), and bronchoalveolar lavage (BAL) was performed. The cultured BAL fluid (BALF) stained with lactophenol cotton blue (figure 2A) and Gram staining (figure 2B) was positive. The metagenomic nextgeneration sequencing (mNGS) showed a high abundance and sequence number of Trichoderma longibrachiatum in the BALF. The patient was then treated with intravenous and oral sequential voriconazole regimen. Her symptoms improved gradually, and the lung lesion on imaging showed slight improvement after 1 month of treatment. As a fungus belonging to the genus Trichoderma, T. longibrachiatum usually exists in humid soil and decaying wood, and is commonly not considered a pathogen in healthy individuals. It has been reported to have the ability to cause invasive infections in immunocompromised hosts. The mortality from T. longibrachiatum infection was as high as 53%. The only identified potential risk factor for T. longibrachiatum infection in our patient was that she had a history of close contact with a pot of Epipremnum aureum, an indoor potted green plant, for more than 1 month before the onset of the disease. The T. longibrachiatum culture of the planting soil was positive. Early diagnosis of T. longibrachiatum is important because the disease has high mortality without treatment, delayed treatment or improper treatment. The clinical presentations of T. longibrachiatum infection are nonspecific. Nowadays,