Extrinsic Allergic Alveolitis



Extrinsic Allergic Alveolitis











Hypersensitivity pneumonitis shows the 2 most important features for its diagnosis: Areas of bronchiolitis obliterans image and the presence of ill-defined granulomas image.






In other areas of lung parenchyma, there is a discrete presence of numerous noncaseating granulomas image. The presence of ill-defined granulomas is characteristic of HP.


TERMINOLOGY


Synonyms



  • Hypersensitivity pneumonitis (HP)


Definitions



  • Granulomatous lung disease secondary to inhalation of organic antigens or chemicals


ETIOLOGY/PATHOGENESIS


Environmental Exposure



  • History of exposure to organic antigens



    • Saccharopolyspora rectivirgula in “farmer’s lung” (moldy hay)


    • Thermoactinomyces sacchari in bagassosis (sugar cane workers)


    • Animal protein from bird feathers and feces from birds


Pathogenesis



  • HP represents immune complex-mediated (type III) T-cell and delayed (type IV) hypersensitivity reaction


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Exact incidence of HP is unknown



      • However, HP may be more prevalent in people exposed to birds


  • Age



    • Usually in adults


  • Gender



    • No predilection for any particular gender


  • Ethnicity



    • No predilection for any particular ethnic group


Site



  • Lung without predilection for specific side or lung segment


Presentation



  • Cough


  • Dyspnea


  • Fever


  • Chills


  • Wheezing


  • Malaise


Laboratory Tests



  • Pulmonary function tests may be abnormal


  • Erythrosedimentation may be elevated


  • C-protein may be elevated


Natural History



  • Acute hypersensitivity pneumonitis



    • 4-6 hours after exposure to antigen


    • Episode may last 12-18 hours


  • Chronic hypersensitivity pneumonitis



    • Patients may have continuous exposure to antigen over months or years


    • Patients may not experience acute episode


    • This type eventually gets biopsied

Jul 9, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Extrinsic Allergic Alveolitis
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