Pulmonary Fibrosis

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Basics

Description

  • 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.
  • The most common idiopathic interstitial pneumonia is idiopathic PF (IPF).
  • 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.

Epidemiology

  • Most common ILD prevalent worldwide accounting for 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
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 favored model for the pathogenesis of IPF is that recurrent, subclinical epithelial damage with accelerated epithelial cell senescence leads to abnormal repair of the alveolus and deposition of interstitial fibrosis by myofibroblasts.
  • Causes of nonidiopathic PF include occupational and environmental exposures, drugs, and connective tissue diseases.
  • IPF pattern on histopathology is UIP, which appears to be a distinct pathophysiologic entity characterized by minimal inflammation and chronic fibroproliferation due to abnormal parenchymal wound healing.

Genetics
  • The role of host genetic factors and their interactions with environmental factors leading to IPF 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, raising birds, hairdressing, stone cutting, exposure to livestock, vegetable and animal dust, and air pollution

General Prevention

It is general avoidance of above noted risk factors.

Commonly Associated Conditions

  • Pulmonary hypertension: 30–80% of patients with IPF
  • GERD
  • Nonidiopathic PF may be related to connective tissue diseases (RA and scleroderma).

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Basics

Description

  • 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.
  • The most common idiopathic interstitial pneumonia is idiopathic PF (IPF).
  • 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.

Epidemiology

  • Most common ILD prevalent worldwide accounting for 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
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 favored model for the pathogenesis of IPF is that recurrent, subclinical epithelial damage with accelerated epithelial cell senescence leads to abnormal repair of the alveolus and deposition of interstitial fibrosis by myofibroblasts.
  • Causes of nonidiopathic PF include occupational and environmental exposures, drugs, and connective tissue diseases.
  • IPF pattern on histopathology is UIP, which appears to be a distinct pathophysiologic entity characterized by minimal inflammation and chronic fibroproliferation due to abnormal parenchymal wound healing.

Genetics
  • The role of host genetic factors and their interactions with environmental factors leading to IPF 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, raising birds, hairdressing, stone cutting, exposure to livestock, vegetable and animal dust, and air pollution

General Prevention

It is general avoidance of above noted risk factors.

Commonly Associated Conditions

  • Pulmonary hypertension: 30–80% of patients with IPF
  • GERD
  • Nonidiopathic PF may be related to connective tissue diseases (RA and scleroderma).

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