Acute necrotizing pneumonia combined with parapneumonic effusion caused by Mycobacterium lentiflavum: a case report

Background: Mycobacterium lentiflavum (M. lentiflavum), a slow growing nontuberculous mycobacterium (NTM), has recently been described as an emerging human pathogen regardless of the immune status of the host. Previous reports have demonstrated that cervical lymphadenitis of children is the most frequent pathology of M. lentiflavum. However, there are little reports regarding pulmonary diseases by M. lentiflavum specifically in immunocompetent patients. Case presentation: A 60-year-old man having prolonged productive cough and dyspnea with fever was initially diagnosed as pneumonia with parapneumonic effusion. Imaging studies showed that the radiologic abnormality was acute bronchopneumonic infiltration with abscess formation in the left lower lobe and parapneumonic pleural effusion. M. lentiflavum was identified in the cultured pleural tissues. On the basis of these findings, he was diagnosed as pulmonary infection and pleurisy caused by M. lentiflavum, which was treated with a combination of antibiotics covering NTM. His clinical manifestations were dramatically improved by the treatment targeting NTM, while those were refractory to empirical antibiotic therapy. Conclusion: In this report, we introduce the isolation of M. lentiflavum from pleural tissues associated with acute necrotizing pneumonia combined with parapneumonic effusion in an immunocompetent host, suggesting that the M. lentiflavum can be a human pathogen invovled in pulmonary infectious diseases and pleurisy with poor response to empirical antibiotic treatment.