Hypersensitivity pneumonitis risk factors

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

The following is a partial list of occupations and major causative antigens that put a patient at risk of HP. Microbial agents like fungi or bacteria in humidifiers, heating systems, and air conditioners found in homes and offices. Exposure to certain chemicals, such as isocyanates or acid anhydrides, can also increase the risk of hypersensitivity pneumonitis in susceptible individuals.

Risk factors

1. Farmers and cattle workers: These workers develop the most common form of HP which is caused by the antigen thermophilic actinomycetes. It is important to note that while Farmer's lung is the most common cause of HP, it still must be distinguished from febrile toxic reactions to inhaled mold dusts (organic dust toxic syndrome, a nonimmunologic reaction) which occurs 30-50 times more often than HP.
2. Poultry and other bird handlers: These workers are exposed to droppings, feathers, and serum proteins of pigeons and other birds.
3. Ventilation workers and those exposed to water-related contamination: These workers may be exposed to microorganisms thatcolonize humidifiers, forced-air systems, hot tubs, whirlpools, and spas. The putative antigens are derived from Thermoactinomyces or Cladosporium.
4. Veterinarians and animal handlers: These workers obviously have daily contact with a large variety of animals and organic antigens.
5. Grain and flour processors and loaders: These workers are exposed to grain. Grain can become colonized with a variety of microorganisms and their antigens.
6. Lumber mill workers and paper and wallboard manufacturers: These workers are exposed to wood which can become colonized with molds and then becomes aerosolized.
7. Plastic manufacturers, painters, and electronics industry workers: These workers can be exposed to diphenylmethane diisocyanate or toluene diisocyanate.
8. Textile workers: These workers do develop lung injury but this is not a true form of HP. The injury is characterized by diffuse alveolar damage or airway dysfunction and includes diseases such as byssinosis and nylon worker's lung.

Hypersensitivity Pneumonitis (HP) may also be called many different names, based on the provoking antigen. These include:

1. Bird-Breeder's Lung : Also called Bird fancier's lung, Pigeon-Breeder's Lung, and Poultry-Worker's Lung. Caused by avian proteins. Exposure is from feathers and bird droppings.

Farmer's Lung

Caused by the molds Thermophilic actinomycetes, Aspergillus species, Saccharopolyspora rectivirgula, and Micropolyspora faeni. Exposure is generally from moldy hay but may be found elsewhere.

Bagassosis

Caused by Thermophilic actinomycetes. Exposure is from moldy bagasse (pressed sugarcane).

Malt Worker's Lung

Caused by Aspergillus clavatus. Exposure is from moldy barley.

Humidifier Lung

Caused by the bacterias T. candidus, Bacillus subtilis, B. cereus, and Klebsiella oxytoca; the fungus Aureobasidium pullulans; and the amoebae Naegleria gruberi, Acanthamoeba polyhaga, and Acanthamoeba castellani. Exposure is from mist from standing water.

Mushroom Worker's Lung

Caused by Thermophilic actinomycetes. Exposure is from mushroom compost.

Compost Lung

Caused by Aspergillus. Exposure is from compost.

Peat Moss Worker's Lung

Caused by Monocillium sp. and Penicillium citreonigrum. Exposure if from peat moss.

Suberosis

Caused by Penicillum frequentans. Exposure is from moldy cork dust.

Japanese Summer-Type HP

Caused by Trichosporon cutaneum. Exposure is from damp wood and mats.

Cheese-Washer's Lung

Caused by Pencillum casei or P.roqueforti. Exposure is from cheese casings.

Metalworking Fluids HP

Caused by Nontuberculous Mycobacteria. Exposure is from mist from metalworking fluids.

Hot Tub Lung

Caused by Mycobacterium avium complex. Exposure is from mist from hot tubs.

Mollusc Shell HP

Caused by aquatic animal proteins. Exposure is from mollusc shell dust.

Isocyanate HP

Caused by TDI, HDI, and MDI. Exposure is from paints, resins, and polyurethane foams.

TMA HP

Caused by Trimellitic anhydride. Exposure is from plastics, resins, and paints.

Berylliosis

Caused by Beryllium. Exposure in the electronics industry.

Wine-grower's lung

From Botrytis cinerea mold on grapes.

Of these types, Farmer's Lung and Bird-Breeder's Lung are the most common. "Studies document 8-540 cases per 100,000 persons per year for farmers and 6000-21,000 cases per 100,000 persons per year for pigeon breeders. High attack rates are documented in sporadic outbreaks. Prevalence varies by region, climate, and farming practices. HP affects 0.4-7% of the farming population. Reported prevalence among bird fanciers is estimated to be 20-20,000 cases per 100,000 persons at risk."