Sometimes doctors can find out what is causing pulmonary fibrosis (lung scarring). For example, exposure to environmental pollutants and certain medicines can cause the disease.
Environmental pollutants include inorganic dust (silica and hard metal dusts) and organic dust (bacteria and animal proteins).
Medicines that are known to cause pulmonary fibrosis in some people include nitrofurantoin (an antibiotic), amiodarone (a heart medicine), methotrexate and bleomycin (both chemotherapy medicines), and many other medicines.
In most cases, however, the cause of lung scarring isn’t known. These cases are called idiopathic pulmonary fibrosis (IPF). With IPF, doctors think that something inside or outside of the lungs attacks them again and again over time.
These attacks injure the lungs and scar the tissue inside and between the air sacs. This makes it harder for oxygen to pass through the air sac walls into the bloodstream.
The following factors may increase your risk of IPF:
- Cigarette smoking
- Viral infections, including Epstein-Barr virus (which causes mononucleosis), influenza A virus, hepatitis C virus, HIV, and herpes virus 6
Genetics also may play a role in causing IPF. Some families have at least two members who have IPF.
Researchers have found that 9 out of 10 people who have IPF also have gastroesophageal reflux disease (GERD). GERD is a condition in which acid from your stomach backs up into your throat.
Some people who have GERD may regularly breathe in tiny drops of acid from their stomachs. The acid can injure their lungs and lead to IPF. More research is needed to confirm this theory.