Causes of Interstitial Lung Disease and Pulmonary Fibrosis

Interstitial lung disease (ILD) can have many causes. Sometimes the cause is known, while in other cases it cannot be identified.

1. Idiopathic Pulmonary Fibrosis (IPF)

Idiopathic pulmonary fibrosis, or IPF, is lung scarring with no known cause. “Idiopathic” means unknown cause.

Possible risk factors include:

• Smoking
• Dust or workplace exposures
• Viral infections
• Gastroesophageal reflux disease (GERD)
• Genetics or family history
• Older age - over age 50
• Male sex

2. Autoimmune and Connective Tissue Disease Related

Autoimmune diseases occur when the immune system mistakenly attacks healthy tissue. This can cause inflammation and scarring in the lungs. Not everyone with an autoimmune disease develops ILD, but the risk may be higher.

Examples include:

• Rheumatoid arthritis
• Scleroderma
• Lupus
• Sjögren’s syndrome
• Mixed connective tissue disease

3. Occupational or Environmental Exposures

Breathing in harmful dust, smoke, chemicals, or other substances over time can damage the lungs. Examples of harmful substances include:

• Coal dust (Black Lung)
• Silica dust (silicosis) 
• Asbestos (asbestosis)
• Mould or dust from wood, metal, animals, birds (ex. hypersensitivity pneumonitis) 
• Smoke

4. Medication or Treatment-Induced

Some medications and treatments can also cause lung scarring, including certain:

• Chemotherapy drugs
• Antibiotics (ex. Nitrofurantoin)
• Anti-inflammatory medications
• Cardiovascular drugs (ex. Amiodarone) 
• Radiation treatments to the chest

Speak with your healthcare provider if you are concerned about a medication or treatment.

5. Other Causes

Familial Pulmonary Fibrosis (FPF)
FPF is usually diagnosed when two or more biologic family members have pulmonary fibrosis. Genetics may increase the risk, but smoking, environmental exposures, and other health conditions may also.

Sarcoidosis
Sarcoidosis causes clusters of inflamed cells, called granulomas, to form in the lungs. These can stiffen the lungs, narrow the airways, and reduce oxygen exchange. Long-term inflammation may lead to permanent scarring or fibrosis.

Viral infections
Some viral infections may cause lung inflammation, scarring, or poor healing. Examples include COVID-19 and influenza.

Cystic or Airspace Filling ILDs
Some ILDs cause cysts or fill the air sacs with material instead of causing mainly inflammation or scarring.
Cystic ILD: Abnormal air-filled spaces form in the lungs and damage lung tissue. Example: Lymphangioleiomyomatosis (LAM)
Airspace-filling ILD: The air sacs fill with fluid, protein, blood, or inflammatory cells, making it harder for oxygen to enter the blood. Example: Desquamative interstitial pneumonia (DIP)