Pulmonary fibrosis

Pulmonary fibrosis is a condition in which there is diffuse fibrosis of lung parenchyma with a resultant impairment of gas transfer and ventilation-perfusion mismatching.

Fibrosis within the lung may be:

• replacement fibrosis, secondary to disorders such as:
  • infarction
  • pneumonia
  • tuberculosis
• focal fibrosis, in response to irritants such as:
  • silica
  • coal dust
• interstitial fibrosis:
  • cryptogenic (idiopathic) fibrosing alveolitis (idiopathic pulmonary fibrosis (IPF))
  • extrinsic allergic alveolitis

Interstitial lung disease (ILD) consists of a group of pulmonary disorders characterised by inflammation and/or fibrosis of the lung parenchyma associated with progressive dyspnoea that frequently results in end-stage respiratory failure (1):

• most common forms of ILD are idiopathic pulmonary fibrosis (IPF), which accounts for approximately one-third of all cases of ILD, hypersensitivity pneumonitis, accounting for 15% of ILD cases, and connective tissue disease (CTD), accounting for 25% of ILD cases
• typically presents with dyspnoea on exertion
• approximately 30% of patients with ILD report cough
• highest rate of ILD occurs in people aged 80 to 84 years, although the average age at diagnosis is 67 to 72 years
  • is more common in females, but IPF (idiopathic pulmonary fibrosis) affects males about 3 times more often

Diagnosis of ILD principles:

• based on symptoms, physical examination, and additional testing that typically includes chest computed tomography (CT), pulmonary function tests, and serology to evaluate for autoimmune diseases
• lung biopsy may be performed if the diagnosis is unclear.

Treatment of ILD principles:

• depends on the cause and severity of interstitial lung disease
• avoidance of medications known to cause interstitial lung disease should be discontinued
• certain exposures (mould, birds) should be avoided
• medical conditions associated with interstitial lung disease (connective tissue diseases, infections) should be treated
• first-line treatment for IPF
  • reduction of progression of the disease via nintedanib or pirfenidone
• lung transplant may be considered for severe ILD

About 30% to 40% of patients with ILD develop progressive fibrosis which causes respiratory failure and is associated with an average survival of 2.5 to 3.5 years after diagnosis without lung transplant (2)

• there is an average survival of 5.2 to 6.7 years after lung transplant

References:

1. Maher TM. Interstitial Lung Disease: A Review. JAMA. Published online April 22, 2024. doi:10.1001/jama.2024.3669.
2. Varghese AE, Jackson CD, Lanfranco J. What Is Interstitial Lung Disease? JAMA. Published online July 03, 2025.