Pulmonary illness associated with exposure to Mycobacterium-avium complex in hot tub water - Hypersensitivity pneumonitis or infection?

Background: Mycobacterium avium complex is common in water. When aerosolized, it is frequently inhaled but rarely causes illness in healthy people. Hypersensitivity pneumonitis to inhaled aerosols has been described; these aerosols are from several sources of water. The pneumonitis forms are collectively known as humidifier lung; the responsible agent in the water remains uncertain. Purpose: To report five cases of respiratory illness in healthy subjects using hot tubs contaminated with M avium complex. Design: Descriptive case reports. Setting: Consultations in two teaching hospitals. Patients: Five healthy people developed respiratory illnesses characterized by bronchitis, fever, and ''flu-like'' symptoms after using a hot tub. Acute exacerbations of their illness developed within hours of heavy use of the hot tubs. Investigations: A chest radiograph and sputum culture in all, BAL in one, CT scan and lung biopsy in another were performed. Culture of the water of the two hot tubs also was done. Results: Chest radiographs showed interstitial infiltrates or a miliary nodular pattern. Cultures of all sputum samples, the lung biopsy specimens, lung lavage and water samples were positive for M avium complex. The lung biopsy specimen revealed noncaseating granulomas. An patients recovered with no treatment for M avium complex. Conclusion: We conclude that the M avium complex in the water was responsible for the pulmonary illnesses. The symptoms and the results of investigations are more suggestive of a hypersensitivity pneumonitis than of an infection, but no serologic proof of an immunologic reaction to the M avium complex or water was obtained.