Pathology of Restrictive Lung Disease Flashcards
Natural History of Restrictive Lung disease
- Discovery of Abnormal CXR or CT scan
- Dyspnoea - Shortness of breath on exertion or at rest as disease progresses
- Respiratory failure - type 1
- Heart failure
What is Diffuse interstitial lung disease.
Diffuse interstitial lung disease (ILD) isa group of complex disorders that affect the connective tissue (interstitium) that forms the support structure of the alveoli (air sacs) of the lungs.
Define the major classes of restrictive lung disease.
Hypersensitivity Pneumonitis - hyperimmune response to substances that are breathed in causing a immune disorder which affects the lungs.
Sarcoidosis - a multisystem granulomatous disorder of unknown aetiology.
Idiopathic Pulmonary disease - chronic inflammation of the lung due to unknown cause
What is the lung interstitium.
The interstitium of the lung is the connective space around the airways and vessels and the space between the basement membranes of the alveolar walls.
In the normal alveolar wall, most of the alveolar epithelial (pneumocyte) and interstitial capillary endiothelial cell basement membranes are in direct contact.
Describe the functional effects of interstitial lung disease
Reduced Lung Compliance
Stiff Lungs
Low FEV1 & Low FVC but FEV1/FVC normal ratio
Reduced Gas Transfer (Tco or Kco)
Diffusion abnormality
Ventilation/Perfusion Imbalance
When small airways affected by pathology
Describe the aetiology of diffuse alveolar damage (DADS).
Diffuse Alveolar Damage - Associated with:
- Major trauma
- Chemical injury/toxic inhalation
- Circulatory shock
- Drugs
- Infection including viruses - Influenza, Sars Cov2, Sars Cov2
- Auto(immune) disease
- Radiation
- But it can be idiopathic i.e. without a known cause
Describe the pathogenesis of DADS
Two stages of evolution - exudative stage and proliferative.
Histopathology:
Protein rich oedema
Fibrin
Hyaline membranes
Denuded basement membranes
Epithelial proliferation
Fibroblast proliferation
Scarring - interstitium and airspacesstage.
Describe aetiology and pathogenesis of Sarcoidosis
Unknown aetiology
Histopathology of sarcoidosis:
- Epithelioid and giant cell granulomas
- Necrosis/caseation very unusual
- Little lymphoid infiltrate
- Variable associated fibrosis
Describe aetiology and pathogenesis of idiopathic pulmonary disease.
No known cause.
Patchy interstitial chronic inflammation
Type II pneumocyte hyperplasia
Smooth muscle and vascular proliferation
Evidence of old and recent injury
Temporal heterogeneity
Spatial heterogeneity
Proliferating Fibroblastic Foci
Describe aetiology of hypersensitivity pneumonitis.
Hypersensitivity Pneumonitis : The antigens -
- Thermophilic actinomycetes
- Micropolyspora faeni
- Thermoactinomyces vulgaris
- Bird / Animal proteins - faeces, bloom
- Fungi - Aspergillus spp
- Chemicals
- Others
Describe the pathogenesis of HP
- Immune complex mediated combined Type III and Type IV Hypersensitivity reaction.
- Soft centriacinar epithelioid granulomata
- Interstitial pneumonitis
- Foamy histiocytes
- Bronchiolitis obliterans
- Upper zone disease
Describe presentation of HP
Acute Presentation of HP:
- Fever, dry cough, myalgia
- Chills 4-9 hours after Ag exposure
- Crackles, tachyopnoea, wheeze
- Precipitating antibody
Chronic Presentation:
- Insidious
- Malaise, SOB, cough
- Low grade illness
- Crackles and some wheeze
HP can lead to respiratory failure when gas transfer is low so the history is important.
Recall the causes and effects of endstage lung fibrosis/honeycomb lung.
Endstage lung fibrosis/honeycomb lung is caused as a result of the restrictive lung diseases. This is what honeycomb lung looks like and it leaves the lung destroyed and useless.
