Pulmonary Fibrosis

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Description

  • Pulmonary fibrosis (PF) encompasses a group of interstitial lung diseases (ILDs), a family of >200 different lung diseases, characterized by inflammation, cellular proliferation, and fibrosis within lung interstitium and bronchial walls.
  • ILD and PF can both be either idiopathic (without a known cause) or secondary.
  • Idiopathic ILD is called idiopathic interstitial pneumonia. The most common idiopathic interstitial pneumonia is idiopathic PF (IPF).
  • IPF is defined as a form of progressive fibrotic ILD associated with the histologic and/or radiologic appearance of usual interstitial pneumonia (UIP) when other causes have been excluded.

Epidemiology

  • Most common ILD prevalent worldwide (25–30% of all ILD)
  • Most common in men >60 years of age

Incidence

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)

Prevalence

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 (CTDs).

Genetics

  • 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.

Risk Factors

  • 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, mold

General Prevention

Avoidance of above risk factors

Commonly Associated Conditions

  • Pulmonary hypertension: 30–80% of patients with IPF
  • GERD
  • Nonidiopathic PF may be related to CTDs (RA and systemic sclerosis).

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