Kobashi Y, et al. - The clinical aspects of pulmonary Mycobacterium kansasii (M. kansasii) disease are reported via retrospectively evaluating the background, diagnostic methods, laboratory findings, radiological findings, treatment and prognosis in 25 patients [median age: 61 years old (20 males, 5 females)] who satisfied the diagnostic criteria of the American Thoracic Society. In pulmonary M. kansasii disease, the upper lobe, and bilateral lung fields frequently exhibited the radiological changes, but the extent of the lesions was limited within ten segments of the lung. Over half of all patients exhibited infiltration shadows or centrilobular small nodules with bronchiectasis, as well as cavities. Findings suggest the possible presence of radiological findings without cavitary disease described in previous studies in patients with pulmonary M. kansasii disease. Sixteen of 25 patients received combined chemotherapy with 15 exhibiting a favorable effect. Among the remaining 9 patients, 2 patients required surgical treatment, one died of other complications and six received no treatment because of hospital transfer. Based on findings, researchers suggest performing a bronchoscopic examination to reach an accurate diagnosis and performing smear and culture examinations for acid-fast bacilli.