Hypersensitivity pneumonitis (HP) or extrinsic allergic alveolitis (EAA) is a rare immune system disorder that affects the lungs.[1] It is an inflammation of the airspaces (alveoli) and small airways (bronchioles) within the lung, caused by hypersensitivity to inhaled organic dusts and molds.[2] People affected by this type of lung inflammation (pneumonitis) are commonly exposed to the dust and mold by their occupation or hobbies.[2]
Chronic forms reveal additional findings of chronic interstitial inflammation and alveolar destruction (honeycombing) associated with dense fibrosis. Cholesterol clefts or asteroid bodies are present within or outside granulomas.[4] Much like the pathogenesis of idiopathic pulmonary fibrosis, chronic HP is related to increased expression of Fas antigen and Fas ligand, leading to increased epithelial apoptosis activation in the alveoli.[6]
In addition, many patients have hypoxemia at rest, and all patients desaturate with exercise.
| Hypersensitivity pneumonitis | |
|---|---|
| Other names | Allergic alveolitis, bagpipe lung, extrinsic allergic alveolitis (EAA) |
 | |
| High magnification photomicrograph of a lung biopsy taken showing chronic hypersensitivity pneumonitis (H&E), showing mild expansion of the alveolar septa (interstitium) by lymphocytes.[clarification needed] A multinucleated giant cell, seen within the interstitium to the right of the picture halfway down, is an important clue to the correct diagnosis. | |
| Specialty | Respirology |
Hypersensitivity pneumonitis may also be called many different names, based on the provoking antigen. These include:
| Type[15] | 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 [16] |
| Bagassosis Exposure to moldy molasses | Thermophilic actinomycetes[16] | Moldy bagasse (pressed sugarcane) |
| Cephalosporium HP | Cephalosporium | Contaminated basements (from sewage) |
| Cheese-washer's lung | Penicillum casei[16] or P. roqueforti | Cheese casings |
| Chemical worker's lung – Isocyanate HP | Toluene diisocyanate (TDI), Hexamethylene diisocyanate (HDI), or Methylene bisphenyl isocyanate (MDI) | Paints, resins, and polyurethane foams |
| Chemical worker's lung[16] – Trimellitic anhydride (TMA) HP | Trimellitic anhydride[16] | 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 |
| Familial HP Also called Domestic HP | Bacillus subtilis, puffball spores | Contaminated walls |
| Farmer's lung | The molds
The bacteria
| Moldy hay |
| Hot tub lung | Mycobacterium avium complex | Mist from hot tubs |
| Humidifier lung | The bacteria
The fungi The amoebae | Mist generated by a machine from standing water |
| Japanese summer house HP Also called Japanese summer-type HP | Trichosporon cutaneum | Damp wood and mats |
| Laboratory worker's lung | Male rat urine protein | Laboratory rats |
| Lycoperdonosis | Puffball spores | Spore dust from mature puffballs[17] |
| Malt worker's lung | Aspergillus clavatus[16] | Moldy barley |
| Maple bark disease | Cryptostroma corticale[16] | Moldy maple bark |
| Metalworking fluids HP | Nontuberculous mycobacteria | Mist from metalworking fluids |
| Miller's lung | Sitophilus granarius (wheat weevil)[16] | Dust-contaminated grain[16] |
| Mollusc shell HP | 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 HP | Streptomyces albus | Contaminated fertilizer |
| Suberosis | Penicillium glabrum (formerly known as Penicillium frequentans) | Moldy cork dust |
| Tap water HP | 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[18][19] |
| 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. 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."[4]
Treatment[edit]
The best treatment is to avoid the provoking allergen, as chronic exposure can cause permanent damage. Corticosteroids such as prednisolone may help to control symptoms but may produce side-effects.[20]
Additional images[edit]
See also[edit]
https://en.wikipedia.org/wiki/Hypersensitivity_pneumonitis
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