What Is Hypersensitivity Pneumonitis?

Hypersensitivity pneumonitis (HP) is a type of interstitial lung disease that occurs when the lungs are repeatedly exposed to certain antigens leading to inflammation and scarring of the lung parenchyma. It is also called allergic alveolitis or extrinsic allergic alveolitis.

Causes:

HP can be caused by various organic or inorganic antigens but most are caused by organic antigens, e.g., molds or avian antigens.

- Molds: Aspergillus, Penicillium, Fusarium, Cladosporium, Rhizopus, and others

- Avian: Usually from pigeons and budgerigars (parakeets)

- Fungi: Mushrooms

- Bacteria: Thermoactinomyces vulgaris and Saccharopolyspora rectivirgula

- Animal proteins: Dog, cat, cattle, guinea pig, rabbit

- Plant pollens: Western red cedar, mesquite, and maple

- Chemicals: Isocyanates, epoxy resin, platinum salts, beryllium, and others

Symptoms:

The symptoms of hypersensitivity pneumonitis include:

- Cough

- Shortness of breath

- Wheezing

- Chest tightness

- Fever

- Chills

- Fatigue

- Weight loss

Diagnosis:

The diagnosis of HP is based on:

- A detailed history of exposure to potential antigens

- Physical examination

- Chest X-ray

- High-resolution computed tomography (HRCT) of the lungs

- Pulmonary function tests

- Bronchoscopy with bronchoalveolar lavage (BAL)

- Lung biopsy

Treatment:

The treatment of HP depends on the severity of the disease and the causative agent.

- In mild cases, avoiding exposure to the antigen may be sufficient.

- In more severe cases, medications such as corticosteroids, immunosuppressive drugs, or antibiotics may be needed.

Prevention:

The best way to prevent HP is to avoid exposure to the antigens that cause it. This may include:

- Avoiding dusty environments

- Wearing a face mask when working with dusty materials

- Keeping the home and workplace clean and free of mold

- Avoiding contact with animals that may carry the antigen