Interstitial lung disease Flashcards
What comprise the pulmonary interstitium?
- Alveolar lining cells type 1 and 2
* Thin elastin-rich connective component containing capillary blood vessels
What takes place across alveolar walls?
Gas exchange
What are the features of alveolar walls?
- Elastic structure (allowing for ventilation)
* Very thin (allowing gas exchange)
What is the early stage of interstitial lung disease?
Alveolitis - injury with inflammatory cell infiltration
What is associated with acute ILD?
Adult respiratory distress syndrome (ARDS)
What is the late stage of ILD?
Fibrosis
What do the clinical effects of ILD occur due to?
- Hypoxia (respiratory failure)
* Cardiac failure
Is fibrosis in ILD diffuse or localised?
Diffuse fibrosis – localised scarring won’t cause many problems
What are causes of ILD?
- Environmental (minerals, drugs, radiation
- Post-ARDS (post-infective episode)
- Hypersensitivity (mouldy hay, avian proteins)
- Unknown (idiopathic)
- Connective tissue diseases – SLE, rheumatoid
- Idiopathic pulmonary fibrosis (IPF)
How is ILD diagnosed?
Based on clinical features often with biopsy
What are biopsy methods in ILD?
Transbronchial biopsy – special forceps used in bronchoscopy (good for picking up granulomas in the case of TB, sarcoid etc)
Thoracoscopic biopsy – more invasive but more reliable and generates far more tissue
What is lymphocytic interstitial pneumonia?
A cause of ILD
What is lymphocytic interstitial pneumonia associated with?
HIV
What are causes of chronic ILD?
- Idiopathic pulmonary fibrosis (IPF)
- Sarcoidosis
- Extrinsic allergic alveolitis (hypersensitivity pneumonitis)
- Pneumoconiosis
- Connective tissue diseases
What is idiopathic pulmonary fibrosis (IPF) also known as?
Cryptogenic fibrosing alveolitis (CFA) or Usual interstitial pneumonia (UIP)
What is IPF?
Progressive interstitial fibrosis of unknown cause
What are the clinical features of IPF?
- Variable associated inflammation
* Finger clubbing
What is the pathology of IPF?
- Subpleural and basal fibrosis
- Inflammatory component variable
- Terminally lung structure replaced by dilated spaces surrounded by fibrous walls (honeycomb lung)
What is extrinsic allergic alveolitis also known as?
Hypersensitivity pneumonitis
What is EAA?
A chronic inflammatory disease affecting the small airways and interstitium with an allergic origin (type III and IV hypersensitivity mixed allergic response)
What is EAA characterised by?
Occasional granulomas
What allergic responses are involved in EAA?
Mixed allergic response
- Type III - antibody mediated
- Type IV - T cell mediated, granuloma formation
What are causes of EAA?
- Thermophilic bacteria – Farmers lung
- Avian proteins – Bird fanciers lung
- Fungi – Malt workers lung
What is used to diagnose EAA?
- Precipitins (antibodies) often detectable in serum
* Biopsy
What is sarcoidosis?
Multisystem granulomatous disorder of unknown cause
What are clinical features of sarcoidosis?
- Granuloma formation
- Uveitis (inflammation of iris)
- Erythema nodosum
- Lymphadenopathy
- Hypercalcaemia
How is sarcoidosis diagnosed?
- CXR - often see bilateral hilar lymphadenopathy
- Restrictive defect in PFT
- Transbronchial biopsy - granuloma
TB and sarcoidosis both result in granuloma formation. How are the 2 distinguishable from one another?
TB involves necrosis, sarcoidosis does not
What is a common side effect of chronic sarcoidosis?
Fibrosis due to chronic inflammation
In what ways can connective tissue diseases affect the respiratory system?
- Interstitial fibrosis (milder than IPF)
- Pleural effusions
- Rheumatoid nodules
What is a rheumatoid nodule?
A necrotic nodule found in the lung - characteristic of rheumatoid
What is pneumoconiosis?
Lung disease caused by mineral dust exposure
What are examples of pneumoconiosis?
- Asbestosis
- Coal workers lung
- Silicosis
What does pneumoconiosis depend on?
- Particle size (1-5μm)
- Reactivity of particle
- Clearance of particle
- Host response
What is asbestos?
A silicate
What shape are asbestos fibres?
- Serpentine (curved) asbestos fibres relatively safe
* Straight (amphibole) asbestos highly dangerous
What are the effects of asbestos exposure?
- Parietal pleural plaques (only caused by asbestos exposure)
- Interstitial fibrosis (asbestosis)
- Bronchial carcinoma
- Mesothelioma