Nontuberculous mycobacterial pulmonary disease caused by <i>Mycobacterium seoulense</i>

<i>Mycobacterium seoulense</i> was first isolated and reported in Korea in 2007. We report a rare case of nontuberculous mycobacterial (NTM) pulmonary disease caused by <i>M. seoulense</i>. A woman in her mid-90s was referred to our hospital due to bloody sputum. She had medical histories of chronic heart failure and chemoradiotherapy for right small cell lung carcinoma. Chest computed tomography showed a consolidation on the mediastinal side of the right lung following radiotherapy and nodules with bronchiectasis of the right upper and middle lobes. Acid-fast culture tests of sputum were positive for <i>M. seoulense</i>. We are currently treating her with tranexamic acid and carbazochrome sodium sulfonate and conducting careful follow-up. <i>M. seoulense</i> infection may need to be recognized as one of the notable NTM pulmonary diseases presenting with respiratory symptoms and radiological findings.