What is interstitial lung disease (ILD) / pulmonary fibrosis?

Interstitial lung disease (ILD) is a broad category of lung diseases that includes more than 130 disorders characterized by scarring (i.e. “fibrosis”) and / or inflammation of the lungs. ILD accounts for 15% of the cases seen by pulmonologists (lung specialists). Some of the disorders included under the heading of ILD are:

• Idiopathic pulmonary fibrosis
• Connective tissue or autoimmune disease-related pulmonary fibrosis
• Hypersensitivity pneumonitis
• Sarcoidosis
• Eosinophilic granuloma (a.k.a. Langerhan’s cell histiocytosis)
• Chronic eosinophilic pneumonia
• Wegener’s granulomatosis
• Idiopathic pulmonary hemosiderosis
• Bronchiolitis obliterans
• Lymphangioleiomyomatosis

 

What are common symptoms of ILD?

• Shortness of breath with exercise
• Non-productive cough

 

These symptoms are generally slowly progressive, although rapid worsening can also occur. Some people also may have a fever, weight loss, fatigue, muscle and joint pain, and abnormal chest sounds – depending upon the cause.

What happens in the lungs with ILD?

 

In ILD, the tissue in the lungs becomes inflamed and / or scarred. The interstitium of the lung includes the area in and around the small blood vessels and alveoli (air sacs) where the exchange of oxygen and carbon dioxide takes place. Inflammation and scarring of the interstitium disrupts this tissue and leads to a decrease in the ability of the lungs to extract oxygen from the air.

 

The progression of ILD varies from disease to disease and from person to person. It is important to determine the specific form of ILD in patients because what happens over time and the treatment may differ depending on the cause. Importantly, each person responds differently to treatment and close monitoring during treatment is important.

 

What causes ILD?

Some of the known causes of ILD include:
• Connective Tissue or Autoimmune Disease
• Scleroderma / Progressive systemic sclerosis
• Systemic lupus erythematosus
• Rheumatoid arthritis
• Polymyositis / Dermatomyositis
• Occupational and Environmental Exposures
• Inorganic dust (asbestos, silica, hard metals)
• Organic dust (bacteria, animal proteins)
• Gases, fumes
• Drugs and Poisons
• Chemotherapy medications
• Antibiotics (this is rare)
• Radiation therapy
• Infections
• Residue of active infection of any type, or ongoing chronic infections.

 

Some ILDs, while we know a lot about them and how they effect patients, have no known cause. These conditions are termed “idiopathic” (idiopathic meaning “of unknown cause”).
Some examples of these include:

• Idiopathic pulmonary fibrosis
• Idiopathic nonspecific interstitial pneumonitis
• Acute interstitial pneumonia
• Sarcoidosi