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Hypersensitivity Pneumonitis

 Hypersensitivity Pneumonitis



Overview

Hypersensitivity pneumonitis (HP) is a type of allergic reaction that causes inflammation in your lungs. Bacteria, fungi, animal and plant proteins, and other allergens can cause HP. Acute hypersensitivity pneumonitis can get better, but chronic hypersensitivity pneumonitis can cause irreversible lung damage and scarring.

Hypersensitivity pneumonitis (HP) is a type of allergy that causes inflammation in the small air sacs of your lungs (alveoli). Your symptoms can be immediate (acute) and go away quickly, or they may develop over time and become ongoing (chronic).

Chronic hypersensitivity pneumonitis is considered an interstitial lung disease. It can lead to lung scarring over time.

You’re at higher risk for hypersensitivity pneumonitis if you work in certain occupations or are around specific allergens. You’re more likely to develop HP if you:

Work on a farm (for instance, with cattle or vegetables).

Handle animals (veterinarians, bird or poultry handlers).

Process and load grains or flour.

Work in lumber mills or strip wood.

Manufacture wallboard and paper.

Are a metal worker.

Are around bird droppings or feathers. This includes using feather-filled bedding.

Breathe in allergens from humidifiers, heating and air conditioning systems or hot tubs, especially if they aren’t maintained well.

Are between 50 and 70 years old.

Symptoms 

Symptoms of hypersensitivity pneumonitis can be acute or chronic. Acute symptoms come on within a few hours of being around an allergen and last a few hours or days. Chronic symptoms can develop slowly and get worse over time.

Symptoms of acute hypersensitivity pneumonitis

Shortness of breath (dyspnea).

Dry cough.

Chest tightness.

Chills.

Fatigue.

Fever.

Muscle aches.

Symptoms of chronic hypersensitivity pneumonitis

Shortness of breath, especially with exertion or activity.

Cough.

Fatigue.

Weight loss.

Finger or toe clubbing.

Causes

Breathing in substances (allergens) that create an immune reaction in your lungs causes hypersensitivity pneumonitis. Over time, this can damage your lungs and worsen your symptoms. There are over 300 known causes of hypersensitivity pneumonitis, including:

Bacteria.

Molds and fungi.

Certain chemicals and metals.

Animal and plant proteins.

Examples of hypersensitivity pneumonitis

Many allergens cause types of hypersensitivity pneumonitis that go by their own names. Examples of HP include:

Condition : Caused by

Bird fancier’s lung. : Proteins in bird feathers or droppings.

Farmer’s lung. : Mold that grows on hay, straw and grain.

Hot tub lung. : Bacteria in water vapor from hot tubs.

Humidifier lung. : Fungi and bacteria in humidifiers and heating and air conditioning systems.

Cheese worker’s lung (or cheese washer’s lung). :Fungi on cheese.

Bagassosis. :Sugar cane mold dust.

Mushroom worker’s lung. :Dust from fungi

Diagnosis

A healthcare provider diagnoses hypersensitivity pneumonitis based on your symptoms and personal history, physical exam and other tests. They may ask you about your work or living environment to understand if you could be exposed to allergens.

Your provider will listen to your lungs with a stethoscope and check your oxygen level with a device they put on your finger (pulse oximeter). You might also get lung function tests, blood tests or imaging.

To help diagnose hypersensitivity pneumonitis, your provider might perform or order additional tests, including:

Allergy blood tests. A provider takes a small sample of blood from your arm using a needle. A lab tests the sample to see if you have signs of a reaction to the allergens that cause HP (hypersensitivity pneumonitis panel).

Imaging. Chest X-rays and CT scans give your provider images of your lungs so they can look for damage.

Pulmonary function tests. Most lung function tests involve breathing into a tube attached to a machine to measure how well your lungs are working. Your provider may also do blood tests or exercise tests to check your lung function.

Bronchoscopy. A healthcare provider uses a small, flexible tube passed through your nose or mouth to view the inside of your lungs and collect samples.

Treatment

To successfully treat hypersensitivity pneumonitis, you have to stay away from the cause.

Even with medication, HP won’t go away completely if you continue to breathe in the allergen. Chronic HP causes damage that may get worse even if you aren’t exposed to the allergen anymore.

Your provider may prescribe drugs to reduce inflammation, open your airways or increase your oxygen levels.

Corticosteroids or immunosuppressive medications. These medications help reduce inflammation. Specific drugs could include prednisone, mycophenolate or azathioprine.

Anti-fibrotic drugs (pirfenidone and nintedanib). These medications can slow lung scarring.

Pulmonary rehabilitation. Breathing exercises and physical therapy can help make breathing easier.

Oxygen therapy. If you have severe HP, you may need extra oxygen to make sure your blood or tissues are getting enough. It’s delivered through a mask on your face or a tube in your nose.

Lung transplant. If your HP progresses to pulmonary fibrosis, you may need a lung transplant.

Type of Doctor Department: Pulmonologists, Radiologists

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