- Pulmonary fibrosis (PF) is an interstitial lung diseases (ILDs), a family of >200 different lung diseases, characterized by inflammation, cellular proliferation, and/or fibrosis within lung interstitium and bronchial walls. If no cause identified, ILD is called idiopathic interstitial pneumonia.
- The most common idiopathic interstitial pneumonia is idiopathic PF (IPF).
- IPF is defined as a form of chronic fibrosing ILD associated with the histologic and/or radiologic appearance of usual interstitial pneumonia (UIP) when other causes have been excluded.
- Most common ILD prevalent worldwide (25–30% of all ILD)
- Most common in men >60 years of age
Higher in North America and Europe (3 to 9 cases per 100,000 person-years) than in South America and East Asia (fewer than 4 cases per 100,000 person-years)
In the United States, the prevalence has been reported to range from 10 to 60 cases per 100,000.
Etiology and Pathophysiology
- A favored model for the pathogenesis of IPF is that recurrent, alveolar epithelial damage with accelerated cell senescence leads to abnormal cellular repair and deposition of interstitial fibrosis by myofibroblasts.
- Causes of nonidiopathic PF include occupational and environmental exposures, drugs, and connective tissue diseases.
- The role of host genetic factors and their interactions with environmental factors is unknown.
- Mutations in genes involved in maintenance of telomere length are associated with increased risk of IPF.
- An SNP in the MUC5B promoter leads to gene over expression and is associated with increased risk of IPF. However, the mechanism linking MUC5B and IPF is not clear.
- Family history of IPF
- Smoking—most significant association
- GERD, OSA
- Occupational and environmental exposures: wood (pine), metal dusts (lead, brass, steel), farming, birds, hairdressing, stone cutting, exposure to livestock, vegetable and animal dust, air pollution, mold
Avoidance of above risk factors
Commonly Associated Conditions
- Pulmonary hypertension: 30–80% of patients with IPF
- Nonidiopathic PF may be related to connective tissue diseases (RA and scleroderma).
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