Pulmonary Mycobacterium kansasii Disease with Solitary Nodule

We recently encountered two patients with pulmonary Mycobacterium kansasii disease showing a solitary nodule. The patients were 53 and 66 years old and both were male. One patient had underlying diseases. The diagnosis was based on the clinical symptom in one patient and an abnormal chest shadow in the other. The final diagnosis was obtained by bronchoscopy and CT-guided lung biopsy. Antituberculous drugs were administered to one patient. We emphasize the importance of the positive identification of causative microorganisms in patients who present with a solitary nodule including surgical methods to differentiate the infection from lung cancer.