Objective: The purpose of this study was to compare the radiographic features seen at presentation of pulmonary infections caused by Mycobacterium malmoense and Mycobacterium tuberculosis. The correct differential diagnosis has important therapeutic implications.
Materials and methods: The initial radiographs of 16 patients who had proved pulmonary M. malmoense infection were compared with those of 32 age-, sex-, and race-matched patients who had M. tuberculosis infection. The radiographs were analyzed by two radiologists who had no knowledge of the infecting organism. For statistical comparisons, chi 2 and Fisher's exact tests were used.
Results: Radiographic findings seen more often in patients who had M. malmoense infection than in those who had tuberculosis were as follows: cavities larger than 6 cm in diameter were found in six (37%) of 16 vs two (6%) of 32 (p < .01); air-fluid levels within cavities were seen in four (25%) of 16 vs one (3%) of 32 (p < .05); loss of lung volume was observed in 12 (75%) of 16 vs 11 (34%) of 32 (p < .01); and coexistent pneumoconiosis was present in four (25%) of 16 vs none of 32 (p < .01). Air-space shadowing involving more than one bronchopulmonary segment was less common in the M. malmoense group, seen in three (19%) of 16 patients, than in the M. tuberculosis group, seen in 16 (50%) of 32 patients (p < .05).
Conclusion: The radiographic appearances of pulmonary infection caused by M. malmoense differ from those of pulmonary tuberculosis. These differences do not appear to be sufficient to allow a specific diagnosis on the basis of radiographic findings alone.