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
symptoms of EAA
- dyspnoea
- fever
- cough 4-8 hours
after exposure to antigen, resolving after 12-24 hours
what happens if there is repeated exposure to the antigen?
type IV HS reaction
pathological features of EAA
- small granulomas
- lymphocytes in the interstitium
- scanty neutrophils, eosinophils, mast cells
- interstitial fibrosis
- rarely honeycomb lung
which occupations are more prone to asbestos related disease?
- mining
- refining asbestos
- building industry
- dockyards
what does the risk of asbestos disease depend on?
- duration (exposure risk)
- intensity
- type of asbestos exposed to
what are the asbestos-related diseases?
- pleural plaques
- pleural effusions
- asbestosis
- malignant mesothelioma
- carcinoma of the lung
what material are pleural plaques made of?
collagen
what does asbestosis consist of?
- interstitial fibrosis of lungs
- maximal at the lung bases
what PFT pattern do patients with asbestosis have?
restrictive
what are asbestosis bodies?
long, thin fibres coated with haemosiderin and protein to form brown filaments with a bead or drumstick pattern
- present in sputum
