Comparison of chest CT findings between suspected and definite cases of primary pulmonary M. avium complex infection

It is very difficult to treat pulmonary infection with MAC, because we have few effective drugs against this organism. In this situation, an early diagnosis and treatment are very important to manage this disease. We evaluated chest CT scans of the primary pulmonary MAC infection which had no underlying lung diseases and no immunocompromised diseases such as HIV infection. We defined suspected cases of pulmonary MAC infection as cases in which abnormal features of chest CT scans were recognized but frequency of detection of organisms of MAC did not fulfil the diagnostic criteria for atypical mycobacteriosis according to Japanese Mycobacteriosis Research Group of the National Chest Hospitals. CT scans of suspected cases were compared with the definite cases. Results obtained were as follows: 1. In classification by CT scans of primary pulmonary MAC infection, the proportion of localized type and diffuse type was the same both in suspected and definite cases. In localized type, more tuberculosis-like pattern was seen in definite cases. 2. In suspected cases, characteristic features of CT scans of primary pulmonary MAC infection were recognized in the same frequency as in definite cases. 3. In pulmonary tuberculosis-like type, definite cases showed more cavitary lesions than suspected cases. These results showed that a careful long term follow-up of suspected cases with frequent bacteriological tests of sputum and chest CT scannings was important for early diagnosis of primary pulmonary MAC infection.