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- Pulmonary fibrosis (PF) is a part of interstitial lung diseases (ILDs) that is a family of >200 different lung diseases, which are characterized by inflammation, cellular proliferation, and/or fibrosis within lung interstitium and bronchial walls. If no cause identified, ILD is called idiopathic interstitial pneumonia.
- Idiopathic PF (IPF) is one of the most common idiopathic interstitial pneumonia.
- IPF is defined as a specific form of chronic fibrosing interstitial pneumonia limited to the lung and associated with the histologic and/or radiologic appearance of usual interstitial pneumonia (UIP) when other causes have been excluded.
- Most common ILD prevalent worldwide accounting for 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).
Exact prevalence is unknown. In the United States, the prevalence of IPF has been reported to range from 10 to 60 cases per 100,000.
Etiology and Pathophysiology
- Exact inciting factors unknown.
- A widely held hypothesis is that this disorder develops in susceptible individuals following some unknown stimuli, which initiate an uncontrolled cascade of events that evolve to the fibrotic process.
- Causes of nonidiopathic PF include occupational and environmental exposure, drugs, and connective tissue diseases.
- IPF pattern on biopsy is UIP, which appears to be a distinct pathophysiologic entity characterized by minimal inflammation and chronic fibroproliferation due to abnormal parenchymal wound healing.
- The role of host genetic factors and their interactions with environmental factors leading to IPF is unknown.
- Some gene polymorphisms have demonstrated a confirmed (usually weak) association.
- It is postulated that it is autosomal dominant transmission with variable penetrance.
- Family history of IPF
- Smoking—most significant association
- Occupational and environmental exposures: primarily to wood (pine), metal dusts (lead, brass, steel), to farming, raising birds, hairdressing, stone cutting, exposure to livestock, vegetable and animal dust
It is general avoidance of above noted 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).