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

Hypersensitivity Pneumonitis

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.

Pigeon Breeder's Lung and Bird Fancier's Disease

Pigeon Breeder's Lung, first reported by Reed (35) in 1965 is one of the classic forms of hypersensitivity pneumonia (HP). It occurs as a result of intermittent exposure to coops that house pigeons during cleaning. Since these birds are not kept inside the home, the presentation of HP is usually acute and episodic. Similar presentations have been noted in person raising chickens and turkeys for commercial use when cleaning the coops and barns.


Bird Fancier's Lung is a broader category in that inside exposure to numerous domestic and wild birds have been reported to lead to hypersensitivity pneumonia. The exposure is usually to fewer and smaller birds. Antigen exposure is lower but continuous causing presentations that are insidious. These patients may present with extensive fibrosis.


The cause of both diseases is inhalation of avian (bird) antigens from feather bloom and/or droppings in closed environments. Patients present as with other forms of HP; acute, subacute, and chronic (insidious). The chronic form has recently been subgrouped into two types; patients with the initial presentation as chronic or insidious, and those who develop fibrosis after repeated acute episodes. (39)


The entire spectrum of histopathological patterns associated with HP and idiopathic interstitial lung disease may be seen in patients with pigeon breeder's and bird fancier's lung. Open lung biopsies have been interpreted as classic HP with granulomata, NSIP and UIP. (36,39) The UIP presentation seems to occur much more commonly in the insidious or chronic group of patients. Death rates in the UIP presentation are significant despite avoidance and uses of systemic steroids. (39)


Diagnosis of bird fancier's lung revolves around a consistent clinical presentation, environmental exposure to birds, serum precipitins to specific bird antigen. Avoidance of the causative bird antigen should lead to resolution or non-progression of the disease, particularly in the acute and subacute presentations.