The diagnosis is made through clinical judgement using a combination of findings because there does not exist a single, universal diagnostic criteria for the disease. The diagnosis is most commonly ascertained first with a detailed exposure history followed by a battery of clinical tests including: imaging, histopathology, pulmonary function testing, serology, bronchoscopy, and more. In 2020, official guidelines were published by American Thoracic Society, Japanese Respiratory Society, and Asociación Latinoamericana del Tórax which provides a systematic approach to the diagnosis of<unk>  that relies on high-resolution computed tomography. Exposure History A detailed occupational, home and environmental exposure history is the first step in diagnosis. Unfortunately, only 60% of inciting antigens are identified in exposure assessment. Re-exposure to the antigen can help aid in diagnosis. Standardized questionnaires have been created to help in obtaining a exposure history although no official questionnaire has been purported. It has been recommended that the questionnaire administered should be relevant to the region in which the exposure has potentially occurred. Detailed exposure assessments are warranted in the cause of damp indoor environments which have the potential to propagate mold throughout the dwelling. The decision to enlist an industrial hygienist should be made based on the answers to evidence based questions during the environmental assessment. The industrial hygeinst or environmental scientist will make the decision to conduct additional sampling. Types<unk>  may also be called many different names, based on the provoking antigen. These include: Type Specific antigen Exposure Bird fancier's lung Also called bird breeder's lung, pigeon breeder's lung, and poultry worker's lung Avian proteins Feathers and bird droppings Bagassosis Exposure to moldy molasses Thermophilic actinomycetes Moldy bagasse (pressed sugarcane) Cephalosporium<unk>  Cephalosporium Contaminated basements (from sewage) Cheese-washer's lung Penicillum casei or P. roqueforti Cheese casings Chemical worker's lung – Isocyanate<unk>  Toluene diisocyanate (TDI), Hexamethylene diisocyanate (HDI), or Methylene bisphenyl isocyanate (MDI) Paints, resins, and polyurethane foams Chemical worker's lung – Trimellitic anhydride (TMA)<unk>  Trimellitic anhydride Plastics, resins, and paints Coffee worker's lung Coffee bean protein Coffee bean dust Compost lung Aspergillus Compost Detergent worker's disease Bacillus subtilis enzymes Detergent Farmer's lung The molds * Aspergillus species The bacteria * Thermophilic actinomycetes *Thermoactinomyces vulgaris * Saccharopolyspora rectivirgula *Absidia corymbifera *Eurotium amstelodami Moldy hay Hot tub lung Mycobacterium avium complex Mist from hot tubs Humidifier lung The bacteria * Thermoactinomyces candidus * Bacillus subtilis * Bacillus cereus, and Klebsiella oxytoca; * Thermophilic actinomycetes The fungi * Aureobasidium pullulans; The amoebae * Naegleria gruberi, * Acanthamoeba polyhaga, and * Acanthamoeba castellani. Mist generated by a machine from standing water Japanese summer house<unk>  Also called Japanese summer-type<unk>  Trichosporon cutaneum Damp wood and mats Laboratory worker's lung Male rat urine protein Laboratory rats Lycoperdonosis Puffball spores Spore dust from mature puffballs Malt worker's lung Aspergillus clavatus Moldy barley Maple bark disease Cryptostroma corticale Moldy maple bark Metalworking fluids<unk>  Nontuberculous mycobacteria Mist from metalworking fluids Miller's lung Sitophilus granarius (wheat weevil) Dust-contaminated grain Mollusc shell<unk>  Aquatic animal proteins Mollusc shell dust Mushroom worker's lung Thermophilic actinomycetes Mushroom compost Peat moss worker's lung Caused by Monocillium sp. and Penicillium citreonigrum Peat moss Pituitary snuff taker's lung Pituitary snuff Medication (Diabetes insipidus) Sauna worker's lung Aureobasidium, Graphium spp Contaminated sauna water Sequoiosis Aureobasidium, Graphium spp Redwood bark, sawdust Streptomyces<unk>  Streptomyces albus Contaminated fertilizer Suberosis Penicillium glabrum (formerly known as Penicillium frequentans) Moldy cork dust Tap water<unk>  Unknown Contaminated tap water Thatched roof disease Saccharomonospora viridis Dried grass Tobacco worker's lung Aspergillus spp Moldy tobacco Trombone Player's lung (Brass Player's Lung) Mycobacterium chelonae Various Mycobacteria inside instruments Wine-grower's lung Botrytis cinerea mold Moldy grapes Woodworker's lung Alternaria, Penicillium spp Wood pulp, dust 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.<unk>  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." Imaging No single imaging finding is singularly definitive of a diagnosis rather clinicians rely on a constellation of findings. Both chest radiographs and high resolution CT scans can be normal. Chest Radiographs Acute presentation may reveal poorly defined a micro-nodular interstitial pattern and ground-glass opacities in the lower and mid lung zones. In addition to this, subacute presentations may show reticular nodular opacities in mid-to-lower lung zones. Chronic forms may show fibrotic changes and appear like Idiopathic pulmonary fibrosis. High-Resolution Computed Tomography This has become a common diagnostic imaging for the diagnosis and is the modality used in the Official ATS/JRS/ALAT Clinical Practice Guideline. Two forms of<unk>  are fibrotic and non-fibrotic findings on chest CT. The two differ in terms of their diagnostic work up and management although there is overall between them. The non-fibrotic form is typically characterized by ground glass opacities, mosaic attenuation, ill defined centrilobular nodules (<5 mm), and air trapping. The fibrotic form is typicaly characterized by irregular linear opacities/coarse reticulations, traction bronchiectasis, and honeycombing, patchy ground-glass attenuation, centrilobular nodules, and mosaic attenuation. Three-density pattern (head cheese sign) is radiological sign which shows a region of the lung with three or more different types of attenuation which can be typical for the fibrotic type. Histopathology The acute form can be characterized by poorly formed noncaseating interstitial granulomas and mononuclear cell infiltration in a peribronchial distribution with prominent giant cells. The subacute, or intermittent, form produces more well-formed noncaseating granulomas, bronchiolitis with or without organizing pneumonia, and interstitial fibrosis. Much like the pathogenesis of idiopathic pulmonary fibrosis (IPF), chronic<unk>  is related to increased expression of Fas antigen and Fas ligand, leading to increased epithelial apoptosis activation in the alveoli. Cholesterol clefts or asteroid bodies are present within or outside granulomas. Pulmonary Function Testing Pulmonary function tests (PFTs) can generally reveal a restrictive pattern however, either a restrictive or obstructive pattern (or both) may emerge on PFTs. PFTs, therefore, are less useful in making a diagnosis but rather tracking improvement or deterioration in lung function following removal or addition of suspected antigens. They may also demonstrate reduced diffusion capacity of lungs for carbon monoxide (DLCO). Bronchoscopy Bronchoalveolar lavage (BAL) is a reliable way to detect inflammation in the lung airways. Fluid analysis from the lavage extracted from the airways on bronchoscopy often reveals a total elevation in cell count in addition to an elevation in the percentage of T lymphocytes. This is a good way to help exclude other similar lung diseases like sarcoidosis, infection and Idiopathic pulmonary fibrosis. Lung biopsy interstitium is expanded by a chronic inflammatory infiltrate. Two multinucleated giant cells can be seen within the interstitium at left, and a plug of organizing pneumonia at bottom left. Lung biopsies can be diagnostic in cases of chronic<unk> , or may help to suggest the diagnosis and trigger or intensify the search for an allergen. The main feature of chronic<unk>  on lung biopsies is expansion of the interstitium by lymphocytes accompanied by an occasional multinucleated giant cell or loose granuloma. When fibrosis develops in chronic<unk> , the differential diagnosis in lung biopsies includes the idiopathic interstitial pneumonias. This group of diseases includes usual interstitial pneumonia, non-specific interstitial pneumonia and cryptogenic organizing pneumonia, among others. The prognosis of some idiopathic interstitial pneumonias, e.g. idiopathic usual interstitial pneumonia (i.e. idiopathic pulmonary fibrosis), are very poor and the treatments of little help. This contrasts the prognosis (and treatment) for<unk> , which is generally fairly good if the allergen is identified and exposures to it significantly reduced or eliminated. Thus, a lung biopsy, in some cases, may make a decisive difference. Serum Precipitins Assays for serum IgGs can aid in identifying possible antigenic exposures and are used as markers of exposure However there use is limited in making a definitive diagnosis because serum antibody levels are often elevated in those people who are exposed to an antigen but do not have the disease. Up to 90% of people exposed to the antigen have precipitins but only 50% of similarly exposed people who are asymptomatic have the same precipitins. False negatives are often common with serum precipitins because of lack of testing reagents for many antigens. Precipitating IgG antibodies against fungal or avian antigens can be detected in the laboratory using the traditional Ouchterlony immunodiffusion method wherein 'precipitin' lines form on agar plate. The ImmunoCAP technology has replaced this time-consuming, labor-intensive method with their automated CAP assays and FEIA (Fluorescence enzyme immunoassay) that can detect IgG antibodies against Aspergillus fumigatus (Farmer's lung or for ABPA) or avian antigens (Bird Fancier's Lung).
Hypersensitivity pneumonitis
Idiopathic pulmonary fibrosis
Chemical pneumonitis
Acute eosinophilic pneumonia
Diffuse panbronchiolitis
Cryptogenic organizing pneumonia
Atypical pneumonia
Eosinophilic pneumonia