Interstitial lung disease Flashcards
Why is the TLOC reduced in interstitial lung disease?
The alveolar membrane is thickened in interstitial lung disease meaning the carbon monoxide does not diffuse easily from the alveoli into the blood stream.
In interstitial lung disease, would we expect to see a restriction in lung volumes (low FVC)?
Yes
How can we measure hypoxia on exertion and reduced exercise capacity testing?
Exercise tests
6m walk tests or incremental walk tests
What is idiopathic pulmonary fibrosis?
Group of lung diseases which produce interstitial lung damage and ultimately fibrosis and loss of elasticity of the lungs
These key features are suggestive of what condition?
- Collection of fibroblasts
- Thickening of alveolar interstitium
- Destruction of alveoli (honey combing)
- Peripheries and base of lung affected more
- Normal lung tissue next to abnormal lung tissue
Idiopathic pulmonary fibrosis
Epidemiology of idiopathic lung fibrosis?
Most common ILD
Uncommon under 45 and most likely in 70s
Men 3x more likely
Related to smoking or those with a hx of smoking
Pathogenesis of IPF?
- Fibroblasts repair damaged tissue
- Fibroblasts migrate to lungs and become myofibroblasts
- Myofibroblasts deposit collagen in ECM
- In IPF, fibroblasts are resistant to apoptosis
- Myofibroblasts proliferate and form fibroblastic foci
- The thickened tissue leads to lower gas exchange efficiency in the lungs
Presentation of IPF?
- Progressive breathlessness and breathlessness on exertion
- Non-productive cough, tiredness, loss of appetite and weight loss, clubbed fingers
What is a classic thing seen in histology in IPF?
Usual interstitial pneumonia is always seen
Areas of fibrotic lung next to areas of normal lung
Honeycombing at the bases of the lung
What 2 treatments are available for IPF? How do they work?
Whats the prognosis for IPF?
- Pirfenidone: inhibits TGF-b and reduces migration and numbers of myofibroblasts which can damage the lung
- Nintedanib: inhibitor of tyrosine kinase receptors, interferes with processes such as fibroblast proliferation, migration and differentiation
Prognosis is very poor and average survival is 2-3yrs from diagnosis
What is hypersensitivity pneumonitis? How is it caused?
What type of hypersensitivity reaction is it?
In sensitised individuals, repetitive inhalation of allergens provokes a hypersensitivity reaction. IgG antibodies produced by lymphocytes retain memory and on secondary exposure, antigen-antibody complexes are formed and deposit in lungs and are not adequately cleared.
Type III hypersensitivity reaction
How is hypersensitivity pneumonitis diagnosed?
Clinical history is key
Ask about pets, mould, occupation
Specific blood IgG levels can be useful
Lymphocytes are more predominant in airways detected by bronchoalveolar lavage
What clinical features would you expect in the acute and chronic stages of hypersensitivity pneumonitis?
- 4-6h post exposure: fever, rigors, myalgia, dry cough, dyspnoea, fine bibasal crackles
- Chronic: finger clubbing, increasing dyspnoea, weight loss, exertional dyspnoea, type 1 respiratory failure and cor pulmonale
Treatment for hypersensitivity pneumonitis?
Identify and remove allergen
Steroids for acute disease
Chronic respond well to nintedanib
Which connective tissue disease can present as interstitial lung disease with a ‘ground glass appearance on CT scan?’
Systemic sclerosis
