Overview
- Interstitial Lung Disease → group of disorders characterised by inflammation and progressive scarring (fibrosis) of the lungs
- Aetiology → idiopathic pulmonary fibrosis, hypersensitivity pneumonitis (extrinsic allergic alveolitis), pneumoconioses (asbestosis), substance-induced (amiodarone, nitrofurantoin, methotrexate, bleomycin). May be secondary to underlying disease = connective tissue disorders, sarcoidosis, vasculitis
- Extrinsic Allergic Alveolitis ⇒ can occur in people with chronic exposure to bird droppings. Condition caused by hypersensitivity induced lung damage due to a variety of inhaled organic particles. Type III hypersensitivity reaction.
- Coal Worker’s Pneumoconiosis ⇒ occupational lung disease caused by long term exposure to coal dust particles. Most commonly experienced by people in coal mining industry. Typically asymptomatic, however may lead to progressive massive fibrosis which is symptomatic. Causes upper zone fibrosis.
- Idiopathic Pulmonary Fibrosis ⇒ most common type of ILD. When there is no other identifiable cause. Affects mostly men 50-70 years old.
- Upper Zone Fibrosis
- Lower Zone Fibrosis
Making Diagnosis
Clinical Features:
- Progressive Dyspnoea → initally exertional dyspnoea, that progresses to dyspnoea at rest
- Chronic Dry Cough
- Bibasal fine-end inspiratory crackles on auscultation
- Digital Clubbing
- Fatigue
Investigations:
- Spirometry → restrictive lung disease pattern (reduced FEV1, significantly reduced FVC, increased FEV1/FVC ratio >0.7)
- CT Scan (Ix of choice to make diagnosis of IPF) → honeycombing (multiple cystic lesions within the lung parenchyma due to fibrosis, ‘ground glass’ appearance)