Pulmonary Mycobacterium kyorinense infection secondary to cavitary pulmonary tuberculosis

Mycobacterium kyorinense (M. kyorinense) was first reported in patients with pulmonary infection or lymphadenitis in 2009. To date, fewer than 20 cases of pulmonary or extra-pulmonary infections have been reported with the bacterium, and the clinical features remain unclear. We report a case of pulmonary M. kyorinense infection in a 45-year-old man who had a history of cavitary pulmonary tuberculosis seven years ago. The patient visited a hospital due to hemosputum and a prolonged productive cough. Chest computed tomography revealed large and thick-walled cavities, with surrounding parenchymal infiltration in the right upper and lower lung lobes. The microbiological diagnosis of M. kyorinense was based on positive culture results from multiple respiratory tract specimens. The patient's treatment started with antimycobacterial medicines, clarithromycin, moxifloxacin, and intravenous amikacin, in accordance with the drug susceptibility profile and previous case reports. The treatment stabilized the patient's symptoms and improved the thoracic imaging. In addition, the sputum culture was negative after the treatment. We reviewed the literature and summarized the clinical features of M. kyorinense infection in 18 patients. All patients with extrapulmonary infections were immunocompromised. In contrast, pulmonary infection occurred in immunocompetent patients who often had a predisposing lung disease. Cavitary lesions were observed at diagnosis only in patients with prior cystic or cavitary lung disease, including pulmonary tuberculosis. This study contributes to the body of case knowledge of M. kyorinense infection and summarizes the clinical features in the literature.