Pulmonary phaeohyphomycosis due to Exophiala dermatitidis in a patient with pulmonary non-tuberculous mycobacterial infection

A 65-year-old Japanese woman repeatedly withdrew and resumed antibiotics against pulmonary nontuberculous mycobacterial infection caused by Mycobacterium intracellulare for more than 10 years. Although she continued to take medications, her respiratory symptoms and chest computed tomography indicated an enlarged infiltrative shadow in the lingular segment of the left lung that gradually worsened over the course of a year or more. Bronchoscopy was performed and mycobacterial culture of the bronchial lavage fluid was negative, whereas Exophiala dermatitidis was detected. After administration of oral voriconazole was initiated, the productive cough and infiltrative shadow resolved. There are no characteristic physical or imaging findings of E. dermatitidis, and it often mimics other chronic respiratory infections. Thus, when confronting refractory nontuberculous mycobacterial cases, it might be better to assume other pathogenic microorganisms, including E. dermatitidis, and actively perform bronchoscopy.