Pathology of Restrictive Lung Diseases Flashcards
What is the other name for restrictive lung disease?
Interstitial lung disease
What is the lung interstitium?
the connective tissue space around the airways and vessels and the space between the basement membrane of the alveolar walls
What do interstitial lung diseases reduce?
Reduce compliance (without the loss of elastic tissue) and gas exchange
In interstitial lung disease, is compliance reduced in inspiration or expiration and why?
reduced compliance on inspiration is caused by fibrous tissue forming as a result of the inflammation
Explain what you would expect to see in the FEV1, FVC and FEV1/FVC ratio in a patient with interstitial lung disease
Low FEV1 & Low FVC but the FEV1/FVC ratio is normal
What is the main symptom of restricted lung disease?
Dyspnoea
What happens in the acute phase of interstitial lung disease?
diffuse alveolar damage
What are the steps in interstitial lung disease?
Diffuse alveolar damage
oedema (protein rich and watery)
Formation of hyaline membranes
Interstitial inflammation and interstitial fibrosis
What is the hyaline membrane?
a layer of plasma protein precipitate that internally lines the alveoli
What is sarcoidosis?
One of the chronic responses to interstitial lung disease
What type of disorder is sarcoidosis?
a multisystem type 4 hypersensitivity granulomatous disorder
Describe the histopathology of sarcoidosis
- Epithelioid and giant cell granulomas
- Necrosis / caseation very unusual
- Little lymphoid infiltrate
- Variable associated fibrosis
What demographic is most commonly affected by sarcoidosis?
young adults, F>M
What is the incidence of sarcoidosis in the UK?
around 3-4/100,000 in the UK
Where in the world is sarcoidosis incidence low?
low in equatorial regions- sarcoidosis is a disease of temperate climates
How does sarcoidosis present?
- Young adult
- Acute arthralgia
- Erythema nodosum
- Bilateral hilar lymphadenopathy
- Incidental abnormal CXR or CT scan - no symptoms. Look for massive enlargement of the hilar lymph nodes (granulomatous inflammation)
- Can present as SOB & cough or it can be asymptomatic.
how is sarcoidosis managed?
Sarcoidosis is often time limiting and does not require any therapeutic intervention.
Name the two clinical findings which, alongside the history and examination, are diagnostic of sarcoidosis
Raised serum Ca+ and ACE
What is hypersensitivity pneumonitis?
A hypersensitivity reaction to organic molecules/antigens
List some of the organic molecules that can cause hypersensitivity pneumonitis
- Thermophilic actinomycetes (farmers lung)
- Bird/ animal proteins e.g. faeces
- Fungi (e.g. aspergillus)
- Chemicals
How does hypersensitivity pneumonitis present?
highly variable
can present like an acute pneumonia but it is more common for it to have a more chronic presentation with gradually decreasing pulmonary function
What are the inflammatory process associated with hypersensitivity pneumonitis driven by?
combined Type III and Type IV Hypersensitivity
What are the type 3 and type 4 hypersensitivities responsible for individually?
The type 4 reaction results in the granuloma formation
type three reaction results in the chronic interstitial inflammatory process (pneumonitis)
How do the hypersensitivity pneumonitis granulomas differ from sarcoidosis granulomas?
hypersensitivity pneumonitis granulomas are soft, diffuse, surrounded by an inflammatory infiltrate, centriacinar & epithelioid in nature
Other than the soft granulomas, what are the 3 other histological features of hypersensitivity pneumonitis?
- Interstitial pneumonitis
- Foamy histiocytes
- Bronchiolitis obliterans
Where in the lungs would hypersensitivity pneumonitis affect most significantly and why?
Upper zones (because it is caused by inhaled antigens)
What is usual interstitial pneumonitis?
Patchy interstitial inflammation with type 2 pneumocyte hyperplasia, proliferative fibroblastic foci and smooth muscle & vascular proliferation
What are the causes of usual interstitial pneumonitis?
- Connective tissue diseases; esp. scleroderma and rheumatoid disease
- Drug reaction
- Post infection
- Industrial exposure - asbestos
- Most are idiopathic
What demographic is affected by idiopathic pulmonary fibrosis?
Elderly >50
M>F
How does idiopathic pulmonary fibrosis present?
- dyspnoea, cough,
- basal crackles, cyanosis, clubbing
What CXR findings would you expect in a patient with idiopathic pulmonary fibrosis?
- Basal/posterior pathology
- Diffuse infiltrates
- Cysts
- ‘Ground glass ’ appearance
