Progressive interstitial fibrosis of unknown cause

Aetiology

• Most common in males and smokers
• More common in older people (median age of presentation 70 years)
• Exact cause unknown

Pathophysiology

• Repetitive injury to the alveolar epithelium, caused by currently unidentified environmental stimuli, leads to the activation of repair pathways
• The the wound healing mechanisms become uncontrolled, leading to subpleural and basal fibrosis
• Terminally, lung structure is replaced by dilated spaces surrounded by fibrous walls - ‘honeycomb’

Clinical features

Symptoms

• Progressive dyspnoea
• Dry cough
• Weight loss
• Fatigue
• Malaise

Signs

• Clubbing
• Cyanosis
• Bilateral fine inspiratory crackles