Interstitial Lung Disease Flashcards
what is interstitial lung disease
disease where there is diffuse parenchymal lung injury/inflammation leading to fibrosis
common features of interstitial lung disease
- dry cough
- breathlessness
- restrictive PFT pattern
- reticulonodular shadowing on CXR and HRCT
why does the restrictive pattern happen?
- reduced expansion of the lung parenchyma
radiological features of interstitial lung disease
- bilateral basilar reticular abnormalities
- ground-glass appearance on HRCT thorax
why is finding out the cause of interstitial lung disease important?
- treatment for one cause may be disastrous for another
pathogenesis of interstitial lung disease
- epithelial injury leading to fibroblast activation, causing fibrosis
- injury to alveolar epithelial cells (smoke, pollutants)
- activation of inflammatory cells and epithelial and endothelial cells
- release of fibrogenic cytokines and growth factors
- proliferation of fibroblast, causes myofibroblast proliferation leading to fibrosis
which are the types of interstitial lung disease?
- exudative
- granulomatous
what happens in exudative interstitial lung disease?
- collagen is laid down on the walls
- this traps the exudates
- affects the base of the lungs
which areas of the lung does granulomatous interstitial lung disease affect?
- spares the base of the lungs
- affects the upper lobes
which are the types of exudative lung disease?
- idiopathic pulmonary fibrosis
- systemic disease like RA, systemic sclerosis
- pneumoconioses
which are the granulomatous lung disease?
- sarcoidosis
- extrinsic allergic alveolitis
- pneumoconioses (silicosis)
signs and symptoms of ILD
- dyspnoea on exertion
- fatigue
- cough
- clubbing
- systemic symptoms: fever, weight loss
- bilateral end-expiratory crackles
- signs of right heart failure
what are the criteria for diagnosis?
- abnormal PFTs with evidence of restriction
- basilar reticular abnormalities with ground-glass appearance on high-resolution CT scans
- lung biopsy of bronchoalveolar lavage showing no features to support an alternative diagnosis
which are the more common types of interstitial lung disease?
- idiopathic pulmonary fibrosis
- extrinsic allergic alveolitis
- asbestos related disease
which group of patients normally present with IPF?
people in their 40s or 50s
which genetic abnormalities are associated with IPF?
- variant of promoter gene that codes for mucin
- mutations in serum surfactant protein C damages type II alveolar epithelial cells
- mutant telomerase
pathogenesis of IPF
- trigger for damage to Type I pneumocyte and alveolar capillary endothelium
- acute phase: interstitial oedema/protein exudation into alveoli (fibrin: early membranes - ARDS picture)
- interstitial inflammation (mainly lymphocytes) and type II pneumocyte regeneration
- fibroblastic activity is stimulated by inflammatory cells, epithelium and endothelium cells releasing cytokines and growth factors
- myofibroblasts secrete extracellular matrix
- resistance of fibroblasts to apoptosis
- organisation leading to interstitial fibrosis
pathological features of a honeycomb lung
- end-stage chronic interstitial fibrosis
- cystic air spaces with coalesence
- dilated bronchi and alveoli
- septal fibrosis and inflammation
- focal squamous metaplasia
- smooth muscle proliferation round terminal bronchioles
commonest causes of honeycomb lung
- idiopathic pulmonary fibrosis
- extrinsic allergic alveolitis
- sarcoidosis
complications of IPF
- fibrosis, reducing the pulmonary capillary network, leading to pulmonary hypertension
- RVH
- RHS HF
prognosis of IPF
- depends on the extent of the fibrosis
what causes extrinsic allergic alveolitis?
- immune reaction to inhaled antigens
- defect in antigen specific T lymphocyte suppressor function
types of EAA
- bird fancier’s lung
- animal handlers’ lung
- farmers’ lung
- microbial antigens (includes contaminated rotting crops)
what type of HS reaction is EAA?
type III
