Pulmonary infection with caseating mediastinal lymphadenitis caused by Mycobacterium gordonae

It is often difficult to discern true mycobacterial infection from colonization due to Mycobacterium gordonae (M. gordonae) since this organism is ubiquitous and is commonly an innocuous saprophyte. This study reports a rare case of caseating hilar adenopathy and pulmonary disease caused by M. gordonae in a patient with chronic obstructive pulmonary disease (COPD) and rheumatoid arthritis (RA) on maintenance steroids and methotrexate. Pathologic exam and cultures of lymph node excision biopsy and bronchoalveolar lavage (BAL) confirmed the diagnosis. Triple antimycobacterial therapy with azithromycin, ethambutol and rifabutin was administered. The patient had significant clinical and radiologic improvement and follow-up cultures confirmed microbiologic cure. Mycobacterium gordonae can be a rare cause of significant pulmonary infection, and positive sputum or BAL cultures for M. gordonae should not be automatically discarded and considered as nonpathogenic contaminants or colonizing organisms, especially in immunocompromised hosts with comorbidities. A detailed review of the case and relevant literature is provided.