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What Is Pulmonary Fibrosis?

Pulmonary Fibrosis (PF) is another chronic lung disease. It presents with symptoms that may resemble COPD. However, PF affects the lungs in a different way than COPD does. It has it’s own diagnostic criteria and it’s own treatment.1 So, what is PF? Here’s all you need to know.

What part of the lung is affected by Pulmonary Fibrosis?

Alveoli are small, balloon-like structures at the end of airways. They are clustered together in large, grape-like clusters. Their walls are made of elastic material. So, like balloons, alveoli expand when filled with air.

Alveolar walls are permeable to oxygen. Their walls also contact with tiny blood vessels called capillaries. Capillary walls are also permeable to oxygen. The space between alveoli and capillaries is called the interstitial space or interstitium. It is here where gas exchange occurs.

Gas exchange like this is an essential component of life. But, there are over 200 diseases that may cause pneumonia and scarring/ fibrosis of this interstitial space. A fancy term for this is “fibrosing interstitial pneumonia.”  All of these diseases are lumped under the umbrella term Interstitial Lung Disease (ILD).2-3

Pulmonary fibrosis is the most common ILD disease.

What causes PF?

A respected theory speculates that some agent directly injures alveolar walls. This causes an abnormal repair process. The end result is that alveolar walls become scarred or fibrotic. This makes alveolar walls thicker and stiffer than normal.2-3

Alveolar walls no longer expand like balloons do. Instead, they become stiff and very difficult to expand. When this happens in large enough areas it can make you feel shortness of breath.

A secondary effect here is it impedes the ability of inhaled oxygen to cross (diffuse) into the bloodstream. This can cause a drop in oxygen levels, which also may cause shortness of breath.

There are various possible causative agents. It may be exposure to dust, fumes, and gases at your work. It may be exposure to cigarette smoke. It may be exposure to drugs, radiation, or asbestos. However, in most instances the cause remains unknown (idiopathic). So, it’s usually diagnosed as Idiopathic Pulmonary Fibrosis.1-7

How is PF like COPD? 

  • Chronic Lung Diseases. They are both diseases that affect the lungs. They are chronic, meaning that they are always present. They are both diseases that are gradually progressive over time. There also is no cure for either.
  • Symptoms. They may present with similar symptoms. These include shortness of breath, chest tightness, coughing, and fatigue. Over time, these may make exertion difficult, and this can make it hard to stay active.
  • Adult Onset. They are both usually diagnosed in adulthood. COPD is usually diagnosed after the ages of 40 or 45. Pulmonary fibrosis is usually diagnosed between the ages of 50 and 70.2
  • Some Treatments. They may both benefit from oxygen therapy, BiPAP therapy, and pulmonary rehabilitation. Another potential treatment for both is lung surgery, such lung transplantation.3-4

How is PF different than COPD? 

  • Prevalence. COPD is a common disease. It affects over 210 million people worldwide and over 16 million US adults.2 However, pulmonary fibrosis is a rare disease. It affects between 132,000 and 200,000 in the US. Because it is so rare, it is often misdiagnosed. One thing it may be misdiagnosed as is COPD.1
  • Fingertips. Both diseases may affect the fingertips. But, how they affect them is different. COPD may cause cyanosis, a bluish discoloration. Pulmonary fibrosis may cause clubbing, which means the nailbeds appear rounded like the reverse side of a spoon.3, 8
  • Medicine. There are many FDA approved medicines used to treat COPD. These medicines are known to reduce symptoms. A class of medicine that proves helpful are corticosteroids. At the present time, there are only 2 FDA approved medicines used to treat PF. COPD medicines like corticosteroids can cause harm for people with PF.1, 3-4, 9
  • Pulmonary Function Testing (PFT). A PFT is a breathing test that can help differentiate COPD from PF. COPD is an obstructive lung disease. Airway obstructions cause airflow limitation that is not reversible. This limitation is what causes that feeling you can’t catch your breath. PF is a restrictive lung disease. It prevents the lungs from fully expanding. Therefore, it affects your diffusing capacity. This means oxygen has a hard time crossing over into your bloodstream.3, 10
  • Diagnosis. X-ray, CT, and PFT can be used to help diagnose both diseases. But, the best test for diagnosing COPD is a PFT. This can confirm airflow limitation that is not reversible. The best test for diagnosing PF may be a lung biopsy. A tissue sample can confirm interstitial pneumonia.

PF affects the lungs differently

PF is a rare lung disease. It affects the lungs in a different way than COPD does, and responds poorly to COPD medicines like corticosteroids. Still, like COPD, there are treatment options for allaying symptoms. And, also like COPD, getting to a proper diagnosis is key to slowing disease progression.


  1. “Pulmonary Fibrosis Patient Guide,” Pulmonary Fibrosis Foundation,, accessesd 7/4/19
  2. Weinberger, Steven E., Barbara A. Cockrill, Jess Mandel, “Principles Of Pulmonary Medicine,” 6th Edition, 2014, Elsevier, pages 153-159
  3. Spagnolo, et al., “Idiopathic Pulmonary Fibrosis: Diagnostic pitfalls and therapeutic challenges,” Multidisciplinary Respiratory Medicine, 2012,, accessed 7/5/19
  4. “Pulmonary Fibrosis: Diagnosis,” Mayo Clinic,, accessed 7/5/19
  5. Olson, et al., The epidemiology of idiopathic pulmonary fibrosis and interstitial lung diseases at risk of a progressive-fibrosing phenotype,” European Respiratory Review, 2018,, accessed 7/4/19
  6. “Pulmonary Fibrosis Overview,” Pulmonary Fibrosis Foundation, “, accessed 7/5/19
  7. “Familial Pulmonary Fibrosis,” National Jewish Hospital,, accessed 7/4/19
  8. “Clubbing of the fingers and toes,” Medline Plus,, accessed 7/5/19
  9. “Idiopathic Pulmonary Fibrosis,” American Thoracis Society,, accessed 7/4/19Chilosi, et al., “The Pathogenesis of COPD and IPF: Distinct horns of the same devil,” Respiratory Researchi, 2012,, accessed 7/5/19