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Biogenics Research Institute
Other Respiratory Tract Disorders
Hypersensitivity Pneumonitis
Idiopathic Intersitial Lung Disease

Mycobacterium Avium Complex (MAC)


MAC is the suspected cause of some cases of hypersensitivity pneumonitis and bronchiolitis. The moist environments of shower stalls and hot tubs combined with naturally occurring MAC can lead to respiratory illnesses that in the past have been associated only with people who are immunosuppressed. Immunosuppression occurs in certain illnesses such as HIV/AIDS, and as the effect of certain medications such as certain cancer treatments. Contaminated hot tubs are now a risk factor for developing MAC respiratory illnesses. (1,2) "Hot tub lung" is a vaguely characterized respiratory disease associated with MAC in hot tubs. Individuals with infections and, or hypersensitivity pneumonitis along with MAC identified in their hot tubs have shown sudden improvement of respiratory symptoms with avoidance of the hot tub. MAC is found in tap water and naturally occurring water. One theory is that the organism is aerosolized in the shower or hot tub and consequently able to penetrate to the deepest parts of the lung. In the reported cases, patients presented with typical symptoms, began standard therapy, and found rapid resolution of symptoms after avoidance of the hot tub or shower. Those with infectious MAC responded to antimicrobial therapy more quickly and dramatically than usual. Those with hypersensitivity pneumonitis were able to discontinue oral corticosteroids with subsequent resolution of illness.


1. Rickman O, et al. Hypersensitivity pneumonitis associated with Mycobacterium avium complex and hot tub use. Mayo Clin Proc. 2002;77:1233-1237.

2. Mary A, et al. Hot tub related Mycobacterium avium intracellulare pneumonitis. Allergy and Asthma Proc. 2002;23:271-273.