Difference between revisions of "Hypersensitivity pneumonitis"

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#redirect [[Diffuse_lung_diseases#Hypersensitivity_pneumonitis]]
{{ Infobox diagnosis
| Name      = {{PAGENAME}}
| Image      =
| Width      =
| Caption    =
| Synonyms  = extrinsic allergic alveolitis
| Micro      = centrilobular prominence of lesions, [[granulomata]], chronic interstitial inflammation consisting primarily of lymphocytes, interstitial fibrosis, air space involvement (alveolitis)
| Subtypes  =
| LMDDx      = [[usual interstitial pneumonia]], [[asbestosis]]
| Stains    =
| IHC        =
| EM        =
| Molecular  =
| IF        =
| Gross      =
| Grossing  =
| Site      = [[lung]] - see ''[[diffuse lung diseases]]''
| Assdx      =
| Syndromes  =
| Clinicalhx = allergen exposure
| Signs      =
| Symptoms  =
| Prevalence = uncommon
| Bloodwork  =
| Rads      = upper lung predominant
| Endoscopy  =
| Prognosis  = usu. good if allergen exposure eliminated
| Other      =
| ClinDDx    = other [[diffuse lung diseases]], esp. [[idiopathic pulmonary fibrosis]]
| Tx        = eliminate allergen exposure
}}
'''Hypersensitivity_pneumonitis''', abbreviated '''[[HP]]''', is a [[diffuse lung diseases]] caused by an allergen.
 
It is also known as '''extrinsic allergic alveolitis''', abbreviated '''EAA'''.
 
==General==
*Exposure to stuffs... e.g. moldy hay - ''Farmer's lung'', atypical mycobacteria - ''hot tub lung''.
*Upper lung predominant disease.
**Mnemonic ''FASSTEN'' - upper lung field: [[Farmer's lung]], [[Ankylosing spondylitis]], [[Sarcoidosis]], [[Silicosis]], [[Tuberculosis]] (miliary), [[Eosinophilic granuloma]], [[Neurofibromatosis]].
*An immune complex-mediated [[hypersensitivity]]<ref name=pmid8279154>{{Cite journal  | last1 = Kaltreider | first1 = HB. | title = Hypersensitivity pneumonitis. | journal = West J Med | volume = 159 | issue = 5 | pages = 570-8 | month = Nov | year = 1993 | doi =  | PMID = 8279154 | url = http://www.ncbi.nlm.nih.gov/pmc/articles/pmid/8279154/?tool=pubmed }}</ref> (Gell-Coombs classification type III).
**If chronic, may develop into a cell-mediated hypersensitivity (Gell-Coombs classification type IV).<ref>URL: [http://library.med.utah.edu/WebPath/EXAM/IMGQUIZ/pufrm.html http://library.med.utah.edu/WebPath/EXAM/IMGQUIZ/pufrm.html]. Accessed on: 4 December 2011.</ref>
 
==Microscopic==
Features:
* Lesions have centrilobular prominence - '''important feature'''. <ref name=pmid16061708/>
** Allergens enter lung through airway which has a centrilobular location.
* [[Granulomata]] (not typically seen in UIP) - '''important feature'''.<ref name=pmid16061708>{{Cite journal  | last1 = Ohtani | first1 = Y. | last2 = Saiki | first2 = S. | last3 = Kitaichi | first3 = M. | last4 = Usui | first4 = Y. | last5 = Inase | first5 = N. | last6 = Costabel | first6 = U. | last7 = Yoshizawa | first7 = Y. | title = Chronic bird fancier's lung: histopathological and clinical correlation. An application of the 2002 ATS/ERS consensus classification of the idiopathic interstitial pneumonias. | journal = Thorax | volume = 60 | issue = 8 | pages = 665-71 | month = Aug | year = 2005 | doi = 10.1136/thx.2004.027326 | PMID = 16061708 }}</ref>
* Chronic interstitial inflammation consisting primarily of lymphocytes.
* Interstitial fibrosis.
* Air space involvement (alveolitis).
 
DDx:
*[[Usual interstitial pneumonia]].
 
===Images===
<gallery>
Image:Hypersensitivity_pneumonitis_low_mag.jpg | Hypersensitivity pneumonitis - low mag. (WC/Nephron)
Image:Hypersensitivity_pneumonitis_intermed_mag.jpg | Hypersensitivity pneumonitis - intermed. mag. (WC/Nephron)
Image:Hypersensitivity_pneumonitis_high_mag.jpg | Hypersensitivity pneumonitis - high mag. (WC/Nephron)
</gallery>
 
==See also==
*[[Diffuse lung diseases]].
 
==References==
{{Reflist|2}}


[[Category:Diagnosis]]
[[Category:Diagnosis]]
[[Category:Diffuse lung diseases]]
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