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Hypersensitivity pneumonitis
Extrinsic allergic alveolitis; Farmer's lung; Mushroom picker's disease; Humidifier or air-conditioner lung; Bird breeder's or bird fancier's lungHypersensitivity pneumonitis is inflammation of the lungs due to breathing in a foreign substance, usually certain types of dust, fungus, or molds.
Causes
Hypersensitivity pneumonitis usually occurs in people who work in places where there are high levels of organic dusts, fungus, or molds.
Long-term exposure can lead to lung inflammation and acute lung disease. Over time, the acute condition turns into long-lasting (chronic) lung disease.
Lung disease
Lung disease is any problem in the lungs that prevents the lungs from working properly. There are three main types of lung disease:Airway diseases -...
Hypersensitivity pneumonitis may also be caused by fungi or bacteria in humidifiers, heating systems, and air conditioners found in homes and offices. Exposure to certain chemicals, such as isocyanates or acid anhydrides, can also lead to hypersensitivity pneumonitis.
Examples of hypersensitivity pneumonitis include:
Bird fancier's lung: This is the most common type of hypersensitivity pneumonitis. It is caused by repeated or intense exposure to proteins found in the feathers or droppings of many species of birds.
Farmer's lung: This type of hypersensitivity pneumonitis is caused by exposure to dust from moldy hay, straw, and grain.
Symptoms
Symptoms of acute hypersensitivity pneumonitis often occur 4 to 6 hours after you have left the area where the offending substance is found. This makes it difficult to find a connection between your activity and the disease. Symptoms might resolve before you go back to the area where you encountered the substance. In the chronic phase of the condition, the symptoms are more constant and are less affected by exposure to the substance.
Symptoms may include:
- Chills
- Cough
- Fever
- Malaise (feeling ill)
Malaise
Fatigue is a feeling of weariness, tiredness, or lack of energy.
Read Article Now Book Mark Article - Shortness of breath
Shortness of breath
Breathing difficulty may involve:Difficult breathing Uncomfortable breathingFeeling like you are not getting enough air
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Symptoms of chronic hypersensitivity pneumonitis may include:
- Breathlessness, especially with activity
- Cough, often dry
- Loss of appetite
- Unintentional weight loss
Exams and Tests
The health care provider will perform a physical examination and ask about your symptoms.
Your provider may hear abnormal lung sounds called crackles (rales) when listening to your chest with a stethoscope.
Lung changes due to chronic hypersensitivity pneumonitis may be seen on a chest x-ray. Other tests may include:
Chest x-ray
A chest x-ray is an x-ray of the chest, lungs, heart, large arteries, ribs, and diaphragm.
- Aspergillosis precipitin blood test to check if you've been exposed to the aspergillus fungus
Aspergillosis precipitin
Aspergillosis precipitin is a laboratory test to detect antibodies in the blood resulting from exposure to the fungus aspergillus.
ImageRead Article Now Book Mark Article - Bronchoscopy with washings, biopsy, and bronchoalveolar lavage
Bronchoscopy
Bronchoscopy is a test to view the airways and diagnose lung disease. It may also be used during the treatment of some lung conditions.
ImageRead Article Now Book Mark Article - Complete blood count (CBC)
CBC
A complete blood count (CBC) test measures the following:The number of red blood cells (RBC count)The number of white blood cells (WBC count)The tota...
ImageRead Article Now Book Mark Article - CT scan of the chest
CT scan of the chest
A chest CT (computed tomography) scan is an imaging method that uses x-rays to create cross-sectional pictures of the chest and upper abdomen....
ImageRead Article Now Book Mark Article - Hypersensitivity pneumonitis antibody blood test
Antibody
An antibody is a protein produced by the body's immune system when it detects harmful substances, called antigens. Examples of antigens include micr...
ImageRead Article Now Book Mark Article - Krebs von den Lungen-6 assay (KL-6) blood test
- Pulmonary function tests
Pulmonary function tests
Pulmonary function tests are a group of tests that measure breathing and how well the lungs are functioning.
ImageRead Article Now Book Mark Article - Surgical lung biopsy
Surgical lung biopsy
An open lung biopsy is surgery to remove a small piece of tissue from the lung. The sample is then examined for cancer, infection, or lung disease....
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Treatment
First, the offending substance must be identified. Treatment involves avoiding this substance in the future. Some people may need to change jobs if they cannot avoid the substance at work.
If you have a chronic form of this disease, your doctor may recommend that you take glucocorticoids (anti-inflammatory medicines). Sometimes, treatments used for asthma can help people with hypersensitivity pneumonitis.
Outlook (Prognosis)
Most symptoms go away when you avoid or limit your exposure to the material that caused the problem. If prevention is made in the acute stage, the outlook is good. When it reaches the chronic stage, the disease might continue to progress, even if the offending substance is avoided.
Possible Complications
The chronic form of this disease may lead to pulmonary fibrosis. This is a scarring of the lung tissue that often is not reversible. Eventually, end-stage lung disease and respiratory failure can occur.
Pulmonary fibrosis
Interstitial lung disease (ILD) is a group of lung disorders in which the lung tissues become inflamed and then damaged.
When to Contact a Medical Professional
Call your provider if you develop symptoms of hypersensitivity pneumonitis.
Prevention
The chronic form can be prevented by avoiding the material that causes the lung inflammation.
References
Patterson KC, Rose CS. Hypersensitivity pneumonitis. In: Broaddus VC, Mason RJ, Ernst JD, et al, eds. Murray and Nadel's Textbook of Respiratory Medicine. 6th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 64.
Tarlo SM. Occupational lung disease. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 87.
Bronchoscopy - illustration
Bronchoscopy is a surgical technique for viewing the interior of the airways. Using sophisticated flexible fiber optic instruments, surgeons are able to explore the trachea, main stem bronchi, and some of the small bronchi. In children, this procedure may be used to remove foreign objects that have been inhaled. In adults, the procedure is most often used to take samples of (biopsy) suspicious lesions and for culturing specific areas in the lung.
Bronchoscopy
illustration
Respiratory system - illustration
Air is breathed in through the nasal passageways, travels through the trachea and bronchi to the lungs.
Respiratory system
illustration
Bronchoscopy - illustration
Bronchoscopy is a surgical technique for viewing the interior of the airways. Using sophisticated flexible fiber optic instruments, surgeons are able to explore the trachea, main stem bronchi, and some of the small bronchi. In children, this procedure may be used to remove foreign objects that have been inhaled. In adults, the procedure is most often used to take samples of (biopsy) suspicious lesions and for culturing specific areas in the lung.
Bronchoscopy
illustration
Respiratory system - illustration
Air is breathed in through the nasal passageways, travels through the trachea and bronchi to the lungs.
Respiratory system
illustration
Review Date: 5/16/2019
Reviewed By: Denis Hadjiliadis, MD, MHS, Paul F. Harron, Jr. Associate Professor of Medicine, Pulmonary, Allergy, and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
