Background: Mycobacterium kansasii is a nontuberculous mycobacterium that can colonize the lungs and cause pulmonary infection. Objective: To report authors' study of 6 patients with pulmonary disease caused by M. kansasii infection in a series of 6 patients diagnosed over 5 years. Method: Between June 1995 and June 2000, 1,349 patients diagnosed with tuberculosis were admitted to the Ipiranga Ari Nogueira da Silva Sanitarium. M. kansasii was identified in the sputum cultures of six (0.44%) of these patients. Results: Patient ages ranged from 25 to 77 years, 5 of the 6 were male, and all presented symptomatic chronic lung disease. All patients tested negative for HIV. Chest radiographs confirmed a history of lung disease; all presented thin walled cavities and adjacent pleural thickening was seen in 2. All patients were initially treated with isoniazid-rifampin-pyrazinamide. In 2 patients, intolerance to pyrazinamide necessitated the substitution of pyrazinamide with ethambutol. Based on the culture results, pyrazinamide was also replaced by ethambutol in 2 other patients. All patients were treated for 9 months or longer, and only one patient suffered recurrence of the disease. After being considered cured of the M. kansasii infection, 1 patient died of respiratory insufficiency due to silicosis. Conclusions: Mycobacteriosis due to M. kansasii was found only rarely and may be attributable to the characteristics of our patients. Therapy with isoniazid, rifampin and pyrazinamide with eventual replacement of the latter by ethambutol was shown to be effective.

Keywords: Mycobacterium kansaii. Lung diseases. Respiratory insufficiency.