[Evaluation of middle lobe syndrome: bronchial washing cultures testing positive for Mycobacterium avium complex]

From 1988 to 1995, a bronchial washing was performed on 118 cases of middle lobe syndrome at the National Himeji Hospital. Twenty cases (16.9%) were positive for Mycobacterium avium complex (MAC). All cases were middle-aged (mean age 54.8), non-smoking women. Fourteen cases were asymptomatic and showed only abnormal shadow on chest X-ray film, while others complained cough, sputum or hemosputum. CT examinations were done on 13 patients, and pulmonary infiltrations were found in addition to right middle lobe or lingula in many cases. It is important to note that MAC infection might be one of causes of middle lobe syndrome.