Tuesday, June 25, 2024
Homebreast cancerWhat Is Hypersensitivity Pneumonitis? Radiology & Treatment

What Is Hypersensitivity Pneumonitis? Radiology & Treatment

What is hypersensitivity pneumonitis and what
are its

Hypersensitivity pneumonitis (HP) is an inflammation of the
lung (usually of the very small airways) caused by the body’s immune
reaction to small air-borne
particles. These particles can be bacteria, mold, fungi, or even
inorganic matter.

What is acute hypersensitivity pneumonitis?

Acute hypersensitivity pneumonitis tends to occur 4-12 hours after exposure (usually heavy exposure) to the particles.

What are the symptoms of acute hypersensitivity pneumonitis?

Symptoms of acute hypersensitivity pneumonitis include:

Chest X-ray may show diffuse small nodules in the lungs. Typically, the symptoms will subside hours to days after exposure (provided there are no repeated exposures). The
abnormalities on chest X-ray abnormalities will also disappear. The
patient’s condition can deteriorate after exposure; therefore it is imperative
that a medical evaluation be performed to determine the best course of

What is chronic hypersensitivity pneumonitis?

Chronic (long-term) hypersensitivity pneumonitis causes
lung scarring (fibrosis).

What are the symptoms of chronic hypersensitivity pneumonitis?

Symptoms of chronic hypersensitivity pneumonitis include:

  • Shortness of breath
  • Cough

Chronic disease is believed to occur after prolonged low grade exposure to the offending particles.
It is sometimes quite surprising that individuals with a passion for their
hobbies or occupation will continue to allow exposure to lung damage (if the
offending particles are related to the hobby or job) despite the knowledge that
it is harmful.

What are examples of hypersensitivity pneumonitis?

Examples of hypersensitivity pneumonitis include:

  • Farmer’s lung disease from exposure to mold spores in hay
  • Pigeon breeder’s disease from exposure to protein particles in
    pigeon droppings
  • Sauna takers’ disease from exposure to mold growing in wet
  • Mushroom workers’ disease from exposure to moldy compost
  • Bagassosis from exposure to moldy sugar cane
  • Winemaker's lung from exposure to a fungus on grapes called
    Botrytis cinerea
  • An unusual case was published involving a case of hypersensitivity to
    Canadian goose dropping
    s. The individual was a physician who was exposed
    to both indoor and outdoor antigens while living in a suburban Illinois
    community. One can only imagine the tremendous detective work necessary to
    make this diagnosis.

A more detailed analysis is listed in the table, which includes the
types of compounds, bacteria, and molds known to cause hypersensitivity

Some Types, Antigens and Exposures That Have Been Identified Disease Name Antigens Exposure Bagassosis

Bacteria (Thermophilic actinomycetes)
Moldy bagasse (pressed sugarcane)

Mushroom worker lung

Bacteria (Thermophilic actinomycetes)
Mushroom compost

Metalworking fluids HP

Bacteria (Mycobacterium immunogenum)
Mist from metalworking fluids

Hot tub HP

Bacteria (Mycobacterium avium complex)
Mist from hot tubs

Lifeguard lung

Bacteria (Endotoxin)
Indoor swimming pool

Farmer’s lung

Bacteria (Thermophilic actinomycetes)
Fungus (Aspergillus species)

Moldy hay

Humidifer lung

Bacteria (T. candidus, Bacillus subtilis, B. cereus, Klebsiella oxytoca)
Fungus (Aureobasidium pullulans)
Amoebae (Naegleria gruberi, Acanthamoeba polyhaga, Acanthamoeba castellani)

Mist from standing water

Compost HP

Fungus (Aspergillus)

Malt worker lung

Fungus (Aspergillus clavatus)
Moldy barley

Peat moss HP

Fungi (Monocillium sp, Penicillium citreonigrum)
Peat moss


Fungus (Penicillum frequentans)
Moldy cork dust

Maple bark HP

Fungus (Cryptostroma corticale)
Moldy wood bark

Wood pulp worker lung

Fungus (Alternaria species)
Moldy wood pulp

Wood trimmer lung

Fungus (Rhizopus species)
Moldy wood trimmings

Tree cutter lung

Fungi (Penicillium (three species), Paecilomyces sp.,
Aspergillus niger, Aspergillus sp., Rhizopus sp.)
Wood chips from living maple and oak trees

Dry rot HP

Fungus (Merulius lacrymans)
Moldy rotten wood


Fungi (Graphium species, Pullularia species)
Moldy wood dust

Japanese summer-type HP

Fungus (Trichosporon cutaneum)
Damp wood and mats

Cheese washer lung

Fungus (Pencillum casei or P.roqueforti)
Cheese casings

Tobacco worker lung

Fungus (Aspergillus sp.)
Moldy tobacco

Greenhouse HP

Fungi (Aspergillus sp., Penicillium sp., Cryptostroma corticale)
Moldy soil

Esparto grass HP

Fungus (Aspergillus fumigatus)
Moldy esparto used to produce ropes, canvas, sandals, mats, baskets, and paper paste

Soy sauce brewer lung

Fungus (Aspergillus oryzae)
Fermentation starter for soy sauce

Bird breeder lung

Avian proteins
Bird droppings and feathers

Mollusc shell HP

Aquatic animal proteins
Mollusc shell dust

Animal handler lung

Animal proteins
urine, serum, fur

Wheat weevil HP

Wheat weevil (Sitophilus granarius)
Infested flour

Silk production HP

Silk worm larvae proteins
Silk worm larvae

Isocyanate HP

Paints, resins, polyurethane foams


Trimellitic anhydride
Plastics, resins, paints

Rose, CS, Lara AR. Hypersenstivity pneumonia In: Mason RJ, Broadus VC, Martin TR, et al. Eds. Murray and Nadel’s Textbook of Respiratory Medicine. 5th ed. Philadelphia, Pa; Saunders Elsevier; 2010; Chap 66.


Allergies can best be described as:
See Answer

How is hypersensitivity pneumonitis diagnosed?

Many people with episodes of hypersensitivity pneumonitis are probably unrecognized and undiagnosed. Some cases believed to be viral pneumonias may actually be hypersensitivity pneumonitis. The patient’s history of repeated episodes of typical symptoms, hours after exposure to certain environments are important in establishing the diagnosis.

Most patients with this disorder have symptoms of shortness of breath and/or cough. Quite often a chest
X-ray may show a variety of abnormalities, but primarily increased lung markings. A specialist in lung disease will primarily depend on a history of exposure either by occupation or hobby. With the abnormal chest X-ray, a high resolution cat scan of the chest is often reviewed. This study shows a detailed image of the appearance of the lung tissue. Lung function tests that examine the lung volumes and the ability for gases to move through the lungs (diffusing capacity) are then performed. Not only are the
CT scan and pulmonary function tests useful in diagnosis but they are also useful in following response to therapy.

Blood antibody tests and skin tests against certain offending molds, bacteria, or particles are available, but their results are usually inconclusive. Other more recent tests such as the serum KL-6 (Krebs von den Lungen-6; this test may act as a marker for activity seen in diffuse lung disease) may be used. Infectious causes as well as collagen vascular diseases and
cancer must be excluded as a cause of the symptoms and signs, and this may involve a biopsy. Unfortunately the small biopsies obtained with a bronchoscope or a needle are usually inadequate. It is often necessary to perform Video Assisted Thoracoscopic Surgery (a.k.a. VATS), which is an open lung biopsy technique performed by thoracic surgeons under general anesthesia. This procedure allows for a larger sample size and more accurate diagnosis.

The interpretation of these tests is complicated, and is best performed by a doctor experienced in hypersensitivity pneumonitis, often with the help of a pathologist experienced in lung diseases. The most accurate determination of the cause of hypersensitivity pneumonitis is almost always a detailed exposure history. It is not uncommon, however, to be unable to find the causative agent.

Latest Lungs News

Trending on MedicineNet

What is the treatment for hypersensitivity pneumonitis?

The most important treatment of hypersensitivity pneumonitis is avoidance of repeated exposures to the offending particles. With early diagnosis and prevention, the prognosis is good. Prolonged, repeated exposures can lead to permanent lung damage, scarring, and potentially significant disability.


Most Popular