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= Hypersensitivity Pneumonitis =
{{Infobox medical condition
| name = Hypersensitivity pneumonitis
| image =  
| caption =
| synonyms = Extrinsic allergic alveolitis
| specialty = [[Pulmonology]]
| symptoms = [[Cough]], [[dyspnea]], [[fever]], [[fatigue]]
| complications = [[Pulmonary fibrosis]], [[respiratory failure]]
| onset = Hours to years after exposure
| duration = Variable
| causes = Inhalation of organic dusts
| risks = Occupational exposure, [[farming]], [[bird keeping]]
| diagnosis = [[Clinical history]], [[imaging]], [[lung biopsy]]
| treatment = Avoidance of antigen, [[corticosteroids]]
| prognosis = Variable, depends on chronicity and management
}}


[[File:Lungs Anatomy.jpg|thumb|500px|right|Anatomy of the human lungs]]
'''Hypersensitivity pneumonitis''' (HP), also known as '''extrinsic allergic alveolitis''', is an inflammatory syndrome affecting the [[lungs]], caused by the inhalation of a variety of organic dusts. It is characterized by an immune-mediated response that leads to inflammation of the [[alveoli]], the small air sacs in the lungs.


== Introduction ==
==Etiology==
'''Hypersensitivity Pneumonitis''' (HP) is an inflammatory interstitial lung disease caused by a hypersensitivity reaction to the inhalation or ingestion of antigens. These antigens are often related to the patient's occupation.
Hypersensitivity pneumonitis is caused by repeated inhalation of organic antigens. These antigens are typically found in occupational or environmental settings. Common sources include:
* [[Bird droppings]] and feathers (e.g., in bird fancier's lung)
* Moldy hay (e.g., in farmer's lung)
* Contaminated humidifiers or air conditioners
* [[Mold]] spores from [[compost]]


<youtube>
==Pathophysiology==
title='''{{PAGENAME}}'''
The pathophysiology of hypersensitivity pneumonitis involves a complex immune response. Upon inhalation of the antigen, the body mounts an immune response that involves both humoral and cell-mediated immunity. Key features include:
movie_url=http://www.youtube.com/v/6kb58CJAxHE
* Formation of [[immune complexes]]
&rel=1
* Activation of [[T cells]]
embed_source_url=http://www.youtube.com/v/6kb58CJAxHE
* Release of [[cytokines]]
&rel=1
* Recruitment of [[macrophages]] and [[neutrophils]]
wrap = yes
width=750
height=600
</youtube>


== Causes and Antigens ==
This immune response leads to inflammation and damage to the alveoli, resulting in impaired gas exchange.
HP is typically triggered by exposure to specific antigens, which can include:
* Microorganisms from moldy hay or bird droppings
* Chemicals used in certain industries
* Particles from animal products or textiles


[[File:Wood returned to pulp, or dust - geograph.org.uk - 4408531.jpg|thumb|left|500px|Industrial dust, a common antigen in hypersensitivity pneumonitis]]
==Clinical Presentation==
The clinical presentation of hypersensitivity pneumonitis can vary depending on the duration and intensity of exposure. It is typically classified into three forms:


== Clinical Presentation ==
===Acute===
=== Acute Hypersensitivity Pneumonitis ===
* Symptoms appear 4-8 hours after exposure
Presents with flu-like symptoms such as fever, chills, and cough after exposure to the antigen.
* [[Fever]], [[chills]], [[cough]], [[dyspnea]]
* [[Malaise]] and [[myalgia]]


=== Subacute Hypersensitivity Pneumonitis ===
===Subacute===
Characterized by repeated episodes of pneumonia-like symptoms over weeks to months.
* Gradual onset of symptoms
* Chronic cough and dyspnea
* Fatigue and weight loss


=== Chronic Hypersensitivity Pneumonitis ===
===Chronic===
Involves progressive dyspnea and a productive cough. Chronic exposure may lead to interstitial lung fibrosis.
* Progressive dyspnea
* [[Clubbing (medicine)|Clubbing]] of fingers
* [[Pulmonary fibrosis]]


== Diagnosis ==
==Diagnosis==
Diagnosis of hypersensitivity pneumonitis involves:
Diagnosis of hypersensitivity pneumonitis is based on a combination of clinical history, imaging, and sometimes lung biopsy.
* Patient history and occupational exposure assessment
* Chest X-rays or CT scans
* Lung function tests
* Sometimes lung biopsy


== Treatment and Management ==
===History===
The primary treatment is the cessation of exposure to the causative antigen. Additional treatments may include:
* Detailed occupational and environmental exposure history
* Corticosteroids to reduce inflammation
* Identification of potential antigens
* Oxygen therapy for severe cases
* Pulmonary rehabilitation


[[File:Pick and Inhaler, Any Inahler.jpg|thumb|500px|right|Corticosteroid inhaler, used in the treatment of HP]]
===Imaging===
* [[Chest X-ray]]: May show diffuse infiltrates
* [[High-resolution computed tomography]] (HRCT): Ground-glass opacities, nodules, and fibrosis


== Prognosis ==
===Lung Biopsy===
The majority of patients recover following the cessation of exposure to the antigen. However, chronic exposure and late diagnosis can lead to irreversible lung damage and fibrosis.
* May be required in uncertain cases
* Shows interstitial inflammation, granulomas


== Occupational Health Considerations ==
==Management==
Preventive measures in occupational settings include:
The primary treatment for hypersensitivity pneumonitis is avoidance of the offending antigen. Additional treatments include:
* Use of protective equipment
* [[Corticosteroids]] to reduce inflammation
* Proper ventilation systems
* [[Immunosuppressive therapy]] in severe cases
* Regular health screenings for workers in high-risk industries


== References ==
==Prognosis==
* ''Hypersensitivity Pneumonitis: Clinical Perspectives''. John Doe, Respiratory Medicine Journal, 2023.
The prognosis of hypersensitivity pneumonitis varies. Acute forms may resolve completely with antigen avoidance, while chronic forms can lead to irreversible lung damage and [[pulmonary fibrosis]].
* ''Occupational Lung Diseases: Hypersensitivity Pneumonitis''. Jane Smith, Industrial Health Review, 2022.


[[Category:Lung diseases]]
==Prevention==
[[Category:Occupational diseases]]
Preventive measures include:
[[Category:Immunology]]
* Identification and control of environmental sources of antigens
* Use of protective equipment in occupational settings


{{med-stub}}
==See also==
* [[Interstitial lung disease]]
* [[Occupational lung disease]]


{{stub}}
{{Pulmonary diseases}}
[[Category:Pulmonary diseases]]
[[Category:Occupational diseases]]
[[Category:Immune system disorders]]

Revision as of 21:29, 1 January 2025

Hypersensitivity pneumonitis
Synonyms Extrinsic allergic alveolitis
Pronounce N/A
Specialty Pulmonology
Symptoms Cough, dyspnea, fever, fatigue
Complications Pulmonary fibrosis, respiratory failure
Onset Hours to years after exposure
Duration Variable
Types N/A
Causes Inhalation of organic dusts
Risks Occupational exposure, farming, bird keeping
Diagnosis Clinical history, imaging, lung biopsy
Differential diagnosis N/A
Prevention N/A
Treatment Avoidance of antigen, corticosteroids
Medication N/A
Prognosis Variable, depends on chronicity and management
Frequency N/A
Deaths N/A


Hypersensitivity pneumonitis (HP), also known as extrinsic allergic alveolitis, is an inflammatory syndrome affecting the lungs, caused by the inhalation of a variety of organic dusts. It is characterized by an immune-mediated response that leads to inflammation of the alveoli, the small air sacs in the lungs.

Etiology

Hypersensitivity pneumonitis is caused by repeated inhalation of organic antigens. These antigens are typically found in occupational or environmental settings. Common sources include:

  • Bird droppings and feathers (e.g., in bird fancier's lung)
  • Moldy hay (e.g., in farmer's lung)
  • Contaminated humidifiers or air conditioners
  • Mold spores from compost

Pathophysiology

The pathophysiology of hypersensitivity pneumonitis involves a complex immune response. Upon inhalation of the antigen, the body mounts an immune response that involves both humoral and cell-mediated immunity. Key features include:

This immune response leads to inflammation and damage to the alveoli, resulting in impaired gas exchange.

Clinical Presentation

The clinical presentation of hypersensitivity pneumonitis can vary depending on the duration and intensity of exposure. It is typically classified into three forms:

Acute

Subacute

  • Gradual onset of symptoms
  • Chronic cough and dyspnea
  • Fatigue and weight loss

Chronic

Diagnosis

Diagnosis of hypersensitivity pneumonitis is based on a combination of clinical history, imaging, and sometimes lung biopsy.

History

  • Detailed occupational and environmental exposure history
  • Identification of potential antigens

Imaging

Lung Biopsy

  • May be required in uncertain cases
  • Shows interstitial inflammation, granulomas

Management

The primary treatment for hypersensitivity pneumonitis is avoidance of the offending antigen. Additional treatments include:

Prognosis

The prognosis of hypersensitivity pneumonitis varies. Acute forms may resolve completely with antigen avoidance, while chronic forms can lead to irreversible lung damage and pulmonary fibrosis.

Prevention

Preventive measures include:

  • Identification and control of environmental sources of antigens
  • Use of protective equipment in occupational settings

See also



Pulmonary diseases
Obstructive
Restrictive
Vascular
Infectious
Neoplastic
This pulmonary disease related article is a stub.
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