Symptoms: Hypersensitivity pneumonitis (HP) presents acutely, as flu-like illness with cough; subacutely, as recurrent "pneumonia"; and chronically, as exertional dyspnea, productive cough and weight loss.
Signs: Most patients have abnormal imaging studies (chest x-ray or high-resolution CT). Crepitant rales are heard in some cases. Pulmonary function testing shows a restrictive defect in early disease and a restrictive, obstructive or mixed defect in late disease. Precipitating antibodies are neither sensitive nor specific, and their presence is no longer considered a hallmark of HP. Some patients have decreased diffusion capacity and arterial hypoxemia. If the diagnosis is in doubt, bronchoalveolar lavage typically shows lymphocytosis. Surgical lung biopsy may be indicated if bronchoscopy is nondiagnostic.
Latency: few weeks to years;
Onset of symptoms after acute exposure: 4 to 12 hours with resolution within a few days;
Repeated exposure to: 1) bioaerosols1 of microbial or animal antigens; or 2) a few reactive chemicals;
Resolution: improvement or complete recovery if exposure terminated early; otherwise, may progress to interstitial fibrosis;
Comments: The current definition of hypersensitivity pneumonitis includes many different diseases with many different etiologies: microbial agents, animal proteins, and chemical sensitizers. A common thread in the most common of these diseases is moldy organic matter or standing water in which potentially invasive2 microorganisms can grow and then become airborne particles in dust or mist. "The respirable conidia of Aspergillus species are ubiquitous in nature and commonly found in water, soil, and organic debris. A variety of Aspergillus species have been associated with HP in persons with diverse occupations, including soy sauce brewers, bird breeders, farmers, and compost, sawmill, mushroom, greenhouse, tobacco, cane mill, grain, and brewery workers, and in those exposed to contaminated esparto grass used in the production of ropes, canvas, sandals, mats, baskets, and paper paste." [Cecile S. Rose In: Murray, p. 1783] Forty-four cases of metalworking fluid HP occurring n ten different plants have been confirmed by lung biopsy. Concentrations of metalworking fluid aerosols in these plants were in most cases below the current OSHA standard. Recent studies have implicated Mycobacteria immunogenum, closely related to M. chelonae, as the causal agent. Improved engineering controls are needed to reduce exposure to metalworking fluids. [Rosenstock, p. 1043-54]
1 A bioaerosol is a suspension of particles of biologic origin in air, either a dust or a mist.
2 Invasive diseases include aspergillosis caused by Aspergillis and mucormycosis, which is mainly caused by Rhizopus. [PPID, p. 3241-53, 3257-66]
| Disease Name | Antigens | Exposure |
|---|---|---|
| Bagassosis | Bacteria (Thermophilic actinomycetes) | Moldy bagasse (pressed sugarcane) |
| Mushroom worker lung | Bacteria (Thermophilic actinomycetes) | Mushroom compost |
| Metalworking fluids HP | Bacteria (Mycobacterium immunogenum) | Mist from metalworking fluids |
| Hot tub HP | Bacteria (Mycobacterium avium complex) | Mist from hot tubs |
| Lifeguard lung | Bacteria (Endotoxin) | Indoor swimming pool |
| Farmer's lung | Bacteria (Thermophilic actinomycetes) Fungus (Aspergillus species) |
Moldy hay |
| Humidifier lung |
Bacteria (T. candidus, Bacillus subtilis, B. cereus, Klebsiella oxytoca) Fungus (Aureobasidium pullulans ) Amoebae (Naegleria gruberi, Acanthamoeba polyhaga, Acanthamoeba castellani) |
Mist from standing water |
| Compost HP | Fungus (Aspergillus) | Compost |
| Malt worker lung | Fungus (Aspergillus clavatus) | Moldy barley |
| Peat moss HP | Fungi (Monocillium sp, Penicillium citreonigrum) | Peat moss |
| Suberosis | Fungus (Penicillum frequentans) | Moldy cork dust |
| Maple bark HP | Fungus (Cryptostroma corticale) | Moldy wood bark |
| Wood pulp worker lung | Fungus (Alternaria species) | Moldy wood pulp |
| Wood trimmer lung | Fungus (Rhizopus species) | Moldy wood trimmings |
| Tree cutter lung | Fungi (Penicillium (three species), Paecilomyces sp., Aspergillus niger, Aspergillus sp., Rhizopus sp.) | Wood chips from living maple and oak trees |
| Dry rot HP | Fungus (Merulius lacrymans) | Moldy rotten wood |
| Sequoiosis | Fungi (Graphium species, Pullularia species) | Moldy wood dust |
| Japanese summer-type HP | Fungus (Trichosporon cutaneum) | Damp wood and mats |
| Cheese washer lung | Fungus (Pencillum casei or P.roqueforti) | Cheese casings |
| Tobacco worker lung | Fungus (Aspergillus sp.) | Moldy tobacco |
| Greenhouse HP | Fungi (Aspergillus sp., Penicillium sp., Cryptostroma corticale) | Moldy soil |
| Esparto grass HP | Fungus (Aspergillus fumigatus) | Moldy esparto used to produce ropes, canvas, sandals, mats, baskets, and paper paste; |
| Soy sauce brewer lung | Fungus (Aspergillus oryzae) | Fermentation starter for soy sauce |
| Bird breeder lung | Avian proteins | Bird droppings and feathers |
| Mollusc shell HP | Aquatic animal proteins | Mollusc shell dust |
| Animal handler lung | Animal proteins | Urine, serum, fur |
| Wheat weevil HP | Wheat weevil (Sitophilus granarius) | Infested flour |
| Silk production HP | Silk worm larvae proteins | Silk worm larvae |
| Isocyanate HP | TDI, HDI, MDI | Paints, resins, polyurethane foams |
| TMA HP | Trimellitic anhydride | Plastics, resins, paints |
References: "Hypersensitivity Pneumonitis" by Cecile Rose in (Murray), "Hypersensitivity Pneumonitis and Organic Dust Toxic Syndromes" by Yvon Cormier and Mark Schuyler in (Asthma in the Workplace), Respiratory Illness in Workers Exposed to Metalworking Fluid Contaminated with Nontuberculous Mycobacteria --- Ohio, 2001, and Mycobacterial Aerosols and Respiratory Disease
See PubMed Abstacts on Hypersensitivity Pneumonitis
Revised May 30, 2018