Interstitial lung disease (ILD): group of lung disordersinclude lung disorders of unknown cause such as IPF and of known causes including connective tissue disease-associated ILD (i.e., related to rheumatoid arthritis, systemic sclerosis...), hypersensitivity pneumonitis and drug-induced ILD characterised by inflammation and/or fibrosis of the lung parenchyma - specifically affecting the interstitium tissue and space surrounding the alveoli - 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 Exclusion of secondary causes is a mandatory step in the diagnosis of IPF. This involves a thorough clinical evaluation to rule out known causes of interstitial lung disease, including environmental or occupational exposures (e.g., mold, birds, asbestos), connective tissue diseases (e.g., rheumatoid arthritis, systemic sclerosis) and drug toxicity (e.g., amiodarone, methotrexate) among others.. [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]
 

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]

 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 

 

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 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

 

• 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 

 

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 ratioForced expiratory volume in 1 sec: forced vital capacity ratio ↓ FVCForced vital capacity
Lung function test - gas transfer (DLCODiffuse capacity of the lungs for carbon monoxide)	Assess gas exchange efficiency	↓ DLCODiffusion capacity of the lungs for carbon monoxide is typical of fibrosis
Chest X-ray		Non-specific findings: Bi-basal  and peripheral reticular opacities ↓ Lung volumes
HRCTHigh-resolution CT thorax	Gold standard imaging	Usual interstitial pneumonia pattern: Traction bronchiectasis Honeycombing Changes are predominantly in basal and peripheral areas

 

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 VATSVideo-assisted thoracoscopic surgery) - most definitive testing
  • Histology: usual interstitial pneumonia pattern

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

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

 

NICE guideline Idiopathic pulmonary fibrosis in adults: diagnosis and management

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