Although IPF gets most of the attention, the other causes of Pulmonary Fibrosis are more common. It is particularly important to diagnose IPF correctly as it is treated very differently from the other causes of Pulmonary Fibrosis.
Pulmonary Fibrosis May be Broadly Divided into 3 Groups.
- Idiopathic: The diagnostic criteria are well described and include a typical pattern on high resolution CT scanning, mostly symmetric (right and left involvement) with worse disease in the lower parts of the lungs, and a paucity of inflammation on imaging. Lung biopsy can sort out cases where the imaging is not diagnostic. Treatment is with either OFEV or Esbriet.
- Pulmonary Fibrosis that responds to immunosuppression: This group includes many different diseases such as non-specific interstitial pneumonitis, respiratory bronchiolitis, desquamative interstitial pneumonitis, hypersensitivity pneumonitis and even sarcoid. This diverse group of lung diseases has many unrelated members, however, they are all at least somewhat responsive to immunosuppression with medications such as prednisone.
- Pulmonary Fibrosis that does not respond to or require immunosuppression: This includes diseases such as scarring from prior lung infections, and pulmonary amyloidosis.
A major challenge for lung specialists that care for patients with interstitial lung diseases is to determine a diagnosis and then map out a treatment plan. In some cases a specific diagnosis is straightforward. In other patients it may be very challenging.
Why is Lung Biopsy Needed?
We receive many questions about why lung biopsy is needed. The short answer is that treating with high-risk medications such as prednisone or mycophenolate should not be undertaken lightly. There are many serious side effects that may occur such as osteoporosis compression fractures, infections, weight gain and others. Imagine treating a patient with an unknown lung disease with prednisone for 6 months only to learn down the road that the diagnosis was IPF—a disease that does not respond to chronic prednisone. I am very wary of embarking on prolonged courses of immunosuppression without at least knowing what family of lung disease I am treating.
For example, it may be hard to separate chronic hypersensitivity pneumonitis from non-specific interstitial pneumonitis. However, both diseases are generally treated the same way so the risk of imprecision is less. On the other hand we must be precise in our diagnosis of IPF versus other lung diseases as OFEV and Esbriet have yet to be shown to be effective in lung diseases other than IPF.