One of the non-IPF causes of pulmonary fibrosis is chronic hypersensitivity pneumonitis. This disease is probably more common than we think. Patients have symptoms of cough and shortness of breath. The disease is slowly progressive for the most part, though there is a form that is more dramatic with fevers and rapidly progressive symptoms.
Causes of Hypersensitivity Pneumonitis
Hypersensitivity pneumonitis is caused by something in the environment (usually your home or work) to which you develop an allergic reaction. But this allergic reaction is not sneezing and nasal congestion but inflammation in your lungs. Some classic examples are allergic reactions to mold in the walls and bird feathers in patients who have birds inside the house. Certain medications may also cause this reaction. Often we are not able to identify the specific cause of the lung process.
Symptoms of Hypersensitivity Pneumonitis
Patients complain of shortness of breath and cough. This leads to a chest xray and eventually a high resolution CT scan of the lungs. This is usually where the diagnosis is first considered. Certain findings can be very suggestive such as air trapping, centrilobular nodules (tiny little nodules in the lungs) and the upper part of the lungs being more involved than the lower part of the lungs. Pulmonary function tests often show a mixed picture of abnormalities.
Bronchoscopy may be helpful in both doing a washing and pinching small biopsies during the procedure. In certain settings the imaging may be diagnostic. In general, most cases of IPF can be distinguished from hypersensitivity pneumonitis though atypical presentations of IPF may have some overlapping characteristics.
If the offending agent can be identified and removed, patients often improve. Other times the disease progresses despite moving homes and our best efforts. Medications such as prednisone and other immunosuppressants are often used with benefit. The chronic form of the disease may not respond fully despite aggressive use of these medications. Patients with more advanced disease may require oxygen and even develop pulmonary hypertension as a result of progressive scarring of the lungs. In some cases lung transplantation is required.