Pathology of Restrictive Lung Disease Flashcards
Where does the inflammtory process of the lungs take place?
The interstitium of the lung
What is the interstitium of the lung?
It is the connective tissue space around the airways and vessels and the the apce between the basement membranes of the alveolar walls of the capillary endothelial.
What makes up the normal alveolar wall?
The alveolar epithelium & interstitial capillary endothelial cell basement membranes are in direct contact.
What are the unifying features of lung disease?
- Disease process involves interstitial area of lung
- All of disease processes are diffuse in the lungs and involving much or all of both lung
- All associated with restrictive lung defect on the pulmonary function testing.
Why do the lungs become stiff (reduced lung compliance)?
Because we are introducing into the interstitial space some kind of pathological tissue (inflammation and fibrous tissue)
What happens to the amount of elastic in interstitial lung disease?
It increases.
What does the interstitial fibro-infammatory process do to the lungs?
It prevents them from stretching.
What does the reduced elasticity of the lung do to the average lung volume?
It decreases.
What does low average lung volume lead to?
It leads to low FEV1 and in turn low FVC
Why is the FEV1/FVC ratio generally the same in interstitial lung disease?
Because there is no airflow limitation.
What happens to gas exchange as a result of interstitial lung disease?
It reduces because there is a diffusion abnormality.
When is there an imbalance in the ventilation/perfusion relationship?
When the pathology affects the small airways.
What is the presentations of diffuse lung disease?
SOB on exertion –> (as disease progresses) shortness of breath at rest.
Respiratory Failure - Type 1
Heart failure
How does the X-ray or CT scan of diffuse lung disease look?
Abnormal
What is an diffuse interstitial lung disease?
They are primarily inflammatory diseases affecting parenchymal part of the lung cause injury within the interstitium of the lung.
What are the two types of inflammatory responses?
Acute (sometimes merge into chronic) and chronic
Where is emphysema normally found?
In the apex of the upper lobe
What happens when emphysema spreads too much?
The lungs get bigger
What is an important factor in interstitial lung disease with regards to the inflammatory process leading to fibrosis?
The more likely the process is to lead to fibrosis, the more likely the patient is going to have long term pulmonary difficulties.
What is acute inflammatory response injury in the lung referred to as pathologically?
It is referred to as diffuse alveolar damage.
What is diffuse alveolar damage related to?
- Trauma
- Chemical injury
- Circulatory Shock
- Drugs
- infection including viruses
- Autoimmune disease
- Radiation
However they can be idiopathic.
What is the process of the development of DAD?
Over 1 or 2 days after injury the is a large amount of oedema that develops in the lungs because there is lots of damage to the interstitial of the lungs. Water and plasma proteins leak out and these plasma proteins precipitate on the alveoli forming hyaline membranes after several more days. It takes a few more days for the inflammatory process to develop and more days for fibrosis to follow on from the inflammatory process.
What are the histological features of DAD?
- Protein rich oedema
- Fibrin
- Hyaline membranes
- Denuded basement membranes
- Epithelial proliferation
- Fibroblast proliferation
- Scarring - interstitial and airspaces
What are examples of a granulomatous chronic inflammatory response in the lung?
Sarcoidosis
Hypersensitivity pneumonitis
What is sarcoidosis?
A multi system granulomatous disorder of unknown aetiology
What type of hypersensitivity reaction is sarcoidosis?
Type IV - production of granuloma
What is the histopathology of sarcoidosis?
- Epihtheliod and giant granulomas
- Necrosis ver unusual
- Little lymphoid infiltrate
- Variable associated fibrosis
Why does sarcoidosis rarely proceed to significant fibrosis?
Because there are very little type III reaction or chronic inflammatory reactions.
What organs are most involved in sarcoidosis?
Lymph nodes and lungs
How is sarcoidosis diagnosed?
Mostly clinically but can be done with imaging
What is hypersensitivity pneumonitis characterised by?
Hypersensitivity reaction to organic molecules or to organic antigens.
What are common antigens of hypersensitivity pneumonitis?
Birds, animals, fungi and chemicals.
What is thermoactinomyces more commonly known as?
Farmers lung
What does the presentation of hypersensitivity pneumonitis depend on?
The reactivity of the patient and the dose of antigen that the patient is exposed to
What is the histopathology of hypersensitivity pneumonitis?
- immune complex mediated combined Type III and IV hypersensitivity reaction
- soft centriacinar epitheliod granulomatoma
- interstitial pneumonitis
- foamy histiocytes
- upper zone disease
What pathological process is taking place in the lungs during idiopathic pulmonary fibrosis?
Usual interstitial pneumonitis
Exposure to what products can lead to idiopathic pulmonary fibrosis?
Drugs, asbestos and viruses
Ho common is it for severe fibrosis to occur in usual interstitial pneumonitis?
Really common
How common is it for granulomatous response to progress to severe fibrosis?
Not common
Diffuse Pulmonary fibrosis is a risk factor for what…
Lung cancer
