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
