Background Information

Definitions

Interstitial lung disease (ILD): group of lung disorders characterised by inflammation and/or fibrosis of the lung parenchyma – specifically affecting the interstitium – leading to impaired gas exchange and progressive dyspnoea. ^[Ref]

Idiopathic pulmonary fibrosis (IPF): most common type of ILD, that is of unknown cause (idiopathic), diagnosed by characteristic clinical, radiologic and/or histopathologic features, and by the exclusion of secondary causes . [Ref]

Usual interstitial pneumonia (UIP) pattern: hallmark radiologic and histopathologic pattern required for the diagnosis of IPF. Radiologically, this includes subpleural & basal lung zone predominant honeycombing (clustered cystic airspaces), traction bronchiectasis and ground-glass opacities. The histological pattern includes a patchy, heterogenous fibrosis of the interstitium. ^[Ref]
 

Epidemiology

IPF is the most common type of ILD → global prevalence of ~18 per 100,000 ^[Ref]

Mean age at diagnosis → ~67-72 years (rare <50 yrs) ^[Ref]

Sex → Male predominant (2-3:1 M:F ratio) ^[Ref]

Risk Factors

 Although the cause of IPF is unknown, there are several risk factors:

•  ↑ Age 
• Male sex 
• Environmental and occupational exposures: ^[Ref] ↑ risk with metal dust, wood dust, pesticides, farrming/agricultural work, asbestos exposure 
• Family History 
• Conditions (may contribute to disease risk / progression)
  • GORD 
  • OSA
  • Lung disease → emphysema / pulmonary hypertension 

 

Clinical Features

IPF presents with typical interstitial lung disease features:

Symptoms 

• Onset → Insidious (over months – years)
• Progressive dyspnoea
  • Initially → extertional 
  • Progresses to dyspnoea at rest 
• Progressive nonproductive cough 
• Nonspecific → weight loss, fatigue 

Signs / Examination findings 

• Inspection → digital clubbing (30-50% of cases), cyanosis (advanced disease)
• Chest auscultation 
  • Fine-inspiratory crackles (velcro-like rales) → indication of pulmonary fibrosis 
    • Distribution → bibasal 
  • Loud inspiratory wheeze (advanced) 

 

 

Complications

• Complications overlap between different types of ILD and include: ^[Ref]
  • Acute exacerbations 
  • Progressive hypoxaemic (type 1) respiratory failure → leading cause of death 
  • Pulmonary hypertension → Cor pulmonale 
  • ↑ risk of lung cancer

 

Prognosis

• Poor prognosis overall (worst of all ILDs)→ median survival of 3-4 years from diagnosis ^[Ref]

 

• Interventions known to improve life expectancy ^[Ref]
  • Antifibrotic therapy (pirfenidone, nintedanib)
  • Lung transplantation 

 

Diagnosis Guidelines

1st Line Tests

Perform ALL the following tests if IPF is suspected.
 

Test	Purpose	Typical findings in IPF
Lung function test – spirometry	To distinguish between obstructive vs restrictive lung disease	IPF causes a restrictive pattern: ↑ FEV1:FVC ratio ↓ FVC
Lung function test – gas transfer (DLCO)	Assess gas exchange efficiency	↓ DLCO is typical of fibrosis
Chest X-ray		Non-specific findings: Bi-basal  and peripheral reticular opacities ↓ Lung volumes
HRCT thorax	Gold standard imaging	Usual interstitial pneumonia pattern: Traction bronchiectasis Honeycombing Changes are predominantly in basal and peripheral areas

 

Further Tests (Specialist)

Specialist tests if diagnosis remains uncertain after 1st line tests:

• Bronchoalveolar lavage
  • Useful to exclude hypersensitivity pneumonitis

 

• Trans-bronchial biopsy (via bronchoscopy)

 

• Surgical lung biopsy (usually via VATS) – most definitive testing
  • Histology: usual interstitial pneumonia pattern

Management Guidelines

General Conservative Management

• Smoking cessation advice
• Offer pulmonary rehabilitation if appropriate
• Oxygen therapy as needed
• Ventilatory support if respiratory failure develops

Pharmacological Management

Symptomatic Management

Management of cough:

• Treat other causes of cough (e.g. GORD, post-nasal drip)
• Opioids, if the cough is debilitating
• Thalidomide – to be considered by a specialist if the cough is intractable

 

Disease-Modifying

Recommended treatment (FVC 50-80% of predicted)

• Nintedanib (small molecule tyrosine kinase inhibitor)
• Pirfenidone (anti-fibrotic and anti-inflammatory agent – via inhibition of TGF-β1)

Oral N‑acetylcysteine is used for managing IPF, but its benefits are uncertain

 

Lung Transplantation

All patients with IPF should be considered for lung transplantation if there are no contraindications

• Discussion and referral should take place 3-6 months after diagnosis or sooner

 

References

Original Guideline