Background: Histological similarity between sarcoidosis and tuberculosis, with epithelioid cell granulomas as the typical finding, suggests that sarcoidosis could be a specific manifestation of infection with mycobacteria. However, convincing evidence for a causal relationship between mycobacterial infection and sarcoidosis has not been produced.
Objective: To examine whether mycobacteria could be cultured from mediastinal lymph nodes from patients with newly diagnosed pulmonary sarcoidosis using a prolonged culture technique.
Methods: The series comprised 15 patients (10 men) with a median age of 45 years (range 25-61) and chest X-ray showing mediastinal lymphadenopathy. The diagnosis of sarcoidosis was based on biopsy specimens of lymph nodes obtained by mediastinoscopy. Lymph node tissue was processed in a prolonged (12 month duration) culture for mycobacteria. Bronchial washings were obtained by bronchoscopy and examined for mycobacteria using fluorescence microscopy, polymerase chain reaction (PCR) for Mycobacterium tuberculosis (M. tuberculosis) DNA and standard culture (7-week duration).
Results: In all lymph node specimens, prolonged culture for mycobacteria was negative. In all bronchial washings, microscopy for mycobacteria, analysis for M. tuberculosis DNA, and standard culture for mycobacteria was negative.
Conclusion: Our study with prolonged culture failed to demonstrate the presence of mycobacteria in sarcoid tissue, especially M. tuberculosis and M. paratuberculosis, and does not suggest that mycobacterial infection could play a direct pathogenic role in patients with pulmonary sarcoidosis.