Case Presentation: A 74-year-old woman presented to the Emergency Department with sudden-onset chest pain and shortness of breath while having a bowel movement. Her history was notable for myeloperoxidase–antineutrophil cytoplasmic antibody–associated interstitial lung disease (ILD), for which she was immunosuppressed on rituximab and hydroxychloroquine, as well as heart failure with mildly reduced ejection fraction (40%) due to ischemic cardiomyopathy. On arrival, she was tachycardic (heart rate 140 beats/min), tachypneic (respiratory rate 26 breaths/min), and hypoxic (oxygen saturation 85% on room air). Her blood pressure was 142/101 mmHg, and she was afebrile.Chest x-ray demonstrated a moderate left pneumothorax with mild rightward mediastinal shift, concerning for early tension physiology. A chest tube was placed emergently, and she was admitted to the progressive care unit. Her hospitalization was prolonged due to a persistent air leak. On hospital day 22, she underwent operative exploration which revealed an approximately 8-mm defect in the left anterolateral lung, repaired with a pledgeted suture. The parietal pleura was covered by a yellow exudative film; samples of this material and pleural tissue were sent for microbiologic and pathologic evaluation. Pathology demonstrated necrotizing granulomatous inflammation with rare acid-fast bacilli, and cultures of the pleural exudate grew Mycobacterium avium complex (MAC). She was started on azithromycin, ethambutol, and rifabutin.Despite surgical repair, the air leak recurred shortly thereafter. She was transferred to a quaternary care center for consideration of bronchoscopic management. Seven endobronchial valves were placed to occlude the left upper lobe and the superior and inferior segments of the lingula. The air leak resolved, and the chest tube was removed. In the following days, she developed worsening dyspnea and a recurrent left pneumothorax. She was transferred to the intensive care unit and placed on high-flow nasal cannula. Complete left lung occlusion was considered, but her advanced ILD limited her respiratory reserve. Goals of care were discussed, and she elected a comfort-focused treatment plan. Shortly thereafter, she died of refractory bronchopleural fistula.
Discussion: Pleural involvement by MAC is rare (1) and most often occurs in the setting of disseminated infection or direct extension from adjacent pulmonary disease. Treatment decisions should be guided by evidence of active pleural or pulmonary disease—such as pleuritis, empyema, or bronchopleural fistula—rather than by organism detection alone.In hospitalized patients with persistent air leak, atypical pleural findings should prompt consideration of nontuberculous mycobacterial infection, particularly in those with underlying structural lung disease or immunosuppression. In our patient, MAC pleuritis was diagnosed based on pleural biopsy and culture of the yellow exudate covering the parietal pleura. We surmise that this infection contributed to the refractory nature of her bronchopleural fistula despite surgical and bronchoscopic interventions.
Conclusions: This case underscores the diagnostic and therapeutic challenges posed by an unusual infectious etiology of persistent air leak and highlights the importance of early multidisciplinary evaluation in patients with complex lung disease.