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- Characterized by fibrosis of the lung parenchyma
- Chest CT shows reticular pattern and honeycombing, with subpleural and lower lobe predominance.
- Lung biopsy shows “usual interstitial pneumonia” pattern.
- Classified based on etiology
- Incidence of IPF is 7 to 16/100,000 person-years.
- Idiopathic pulmonary fibrosis (IPF) is more common in men.
- Most patients with IPF are >60 years.
- Incidence of nonidiopathic pulmonary fibrosis is unknown.
- Prevalence of IPF is 2 to 39 cases/100,000 people.
- Prevalence of nonidiopathic pulmonary fibrosis is unknown.
Etiology and Pathophysiology
- Postulated that microinjury to alveolar epithelial cells causes release of cytokines that activates fibroblasts, which in turn leads to excess production of extracellular matrix
- Causes of the nonidiopathic form include:
- Occupational exposure
- Environmental exposure
- Systemic connective tissue diseases
- Granulomatous diseases
- <5% of IPF is familial and may involve mutations in surfactant protein A2 and C and/or abnormal telomere shortening.
- Most likely mode of transmission is autosomal dominant with variable penetrance.
- Family history of pulmonary fibrosis
- Gastroesophageal reflux disease (GERD)
- Exposure to birds, livestock, dust from metals or wood, solvents
Avoid the risk factors mentioned earlier, such as smoking, certain occupational exposures, or drugs that induce pulmonary fibrosis.
Commonly Associated Conditions
- Pulmonary hypertension: occurs in 30–80% of patients with IPF, likely as a result of hypoxemic vasoconstriction
- Nonidiopathic pulmonary fibrosis may be associated with connective tissue diseases (e.g., rheumatoid arthritis and scleroderma).