Pulmonary fibrosis and other interstitial lung diseases (ILD) occur when scar tissue from a lung injury builds up in the lungs. As the scarring occurs, lungs become stiff, making it difficult to breathe and properly deliver oxygen to the lungs.

ILD factors include idiopathic, environmental or occupational exposures, immune system diseases, drug-related treatment, and genetics.

Idiopathic (Unknown Cause)

Idiopathic interstitial pneumonias (IIPs) include several types of idiopathic lung diseases that may lead to pulmonary fibrosis but differ in their presentation, history, and response to treatments.

Idiopathic pulmonary fibrosis (IPF) is the most common IIP. Other types of IIP include:

• Acute interstitial pneumonia (AIP)
• Respiratory bronchiolitis associated interstitial lung disease (RBILD)
• Desquamative interstitial pneumonia (DIP)
• Non-specific interstitial pneumonia (NSIP)
• Bronchiolitis obliterans with organizing pneumonia (BOOP)

Our doctors have the expertise needed to accurately determine the type of IIP and especially to distinguish IPF from other lung diseases. They are specially trained to determine whether surgical lung biopsy is needed for diagnosis.

Environmental or Occupational Exposures

Inhaling asbestos or silica particles can cause pulmonary fibrosis or ILD years after the original exposure.

Other substances that cause this disease include organic antigens such as bird droppings, molds, fungi, grain dust, wood dust, and chemical irritants such as metal fumes.

Immune System Diseases

Systemic diseases that affect multiple organs in the body can cause pulmonary fibrosis and ILD.

Connective tissue diseases such as rheumatoid arthritis, systemic lupus erythematous, scleroderma, and polymyositis may cause pulmonary fibrosis.

In these diseases, other organs are typically affected before or at the same time as the lungs; blood tests can indicate if the lungs are being affected first.

Drug-Related Treatment

Chemotherapy drugs used to treat cancer (bleomycin, methotrexate, BCNU), treatments for heart rhythm problems (amiodarone), and some antibiotics (nitrofurantoin) commonly cause pulmonary fibrosis.

Genetics

Several genes have been identified that predispose patients to pulmonary fibrosis and ILD. Rare genetic disorders such as Hermansky Pudlack syndrome, dyskeratosis congenita, and neurofibromatosis are associated with pulmonary fibrosis.

Abnormalities in proteins in the lungs as well as proteins that repair damaged DNA predispose people to interstitial lung diseases, especially ones that occur at a younger age.

However, these genetic disorders are rare and do not account for pulmonary fibrosis or ILD in most patients. Our research indicates up to 10 percent of cases of sporadic idiopathic pulmonary fibrosis are in fact familial (defined as two or more case of pulmonary fibrosis in a family), and up to 40 percent of isolated IPF cases share common genetic predispositions found in familial cases.

Learn more about pulmonary fibrosis research at Duke.