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 Diseases

Autoimmune diseases occur when the immune system mistakenly attacks healthy tissue. This can cause inflammation and scarring in the lungs.

Examples include:

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

Not everyone with an autoimmune disease develops ILD, but the risk may be higher.

3. Occupational or Environmental Exposures

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

Examples include:

• Coal dust
• Silica dust
• Asbestos
• Metal, wood, plant, or animal dust
• Smoke
• Birds or livestock
• Certain chemicals or inhaled drugs

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

• Chemotherapy drugs
• Antibiotics
• Anti-inflammatory medications
• Radiation treatments to the chest

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

4. 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)

5. Other Causes

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

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.