Pathology of restrictive lung disease Flashcards
What is the interstitium of the lung
Connective tissue space around the airways and vessels and the space between the basement membranes of the alveolar walls
In a healthy lung, how much interstitial space is there?
Very little, because most of the alveolar epithelial cells and capillary endothelial cell basement membranes are in direct contact
What is the effect of interstitial infiltrate penetrating the alveolar walls?
Reduction in compliance (stiff lungs)
Although the elastic fibres in the alveolar walls still remain, the inflammation means they cannot stretch
How does restrictive (interstitial) lung disease affect FEV1 and FVC values?
Low FVC and low FEV1 values
FEV1/FVC ratio remains normal in most interstitial diseases
(However there are some interstitial lung diseases that are also obstructive and thus the ratio is less than normal)
Aside from changes to FEV1 and FVC values, what are the other effects to the respiratory system?
Reduced gas transfer due to increased diffusion distance - causing reduced Tco or Kco
Ventilation/perfusion imbalance when small airways affected by pathology
How is Restrictive lung disease presented?
Discovery of abnormal CXR
Dyspnoea - either on exertion or at rest depending on severity
Respiratory failure type 1
Heart failure
How can a restrictive lung disease also be obstructive?
Some RLDs also cause bronchiolar inflammation which is obstructive
Will an interstitial lung disease cause an increased or decreased number of ribs visible of a chest x-ray?
Decreased number of ribs as lungs can not expand as much as normal
(Hypoventilation)
What can lead to chronic interstitial inflammation in a patient?
Parenchymal (interstitial) lung injury with either:
- Chronic response
- Acute response which becomes chronic
What are the main types of chronic responses to parenchymal (interstitial) lung disease?
Granulomatous responses
Usual Interstitial pneumonitis UIP
Other patterns of chronic inflammation
All leading to fibrosis or end stage honeycombing
What is DAD?
Diffuse alveolar damage - acute response to parenchymal injury
What are the causes of DAD?
- Major trauma
- Chemical/toxin inhalation
- Circulatory shock
- Drugs
- Infection
- Autoimmune disease
- Radiation
Can be idiopathic
What is the prognosis of DAD?
Not good
High patient mortality
What is the histological features of DAD?
Protein and fibrin rich oedema
Development of hyaline membranes
Denuded basement membranes
Epithelial proliferation
Fibroblast proliferation
Scarring of interstitium and airspaces
What are the types of granulomatous responses?
Sarcoidosis
Hypersensitivity pneumonitis
What is sarcoidosis?
Multisystem granulomatous disorder characterised by:
- epithelioid and giant cell granulomas
- necrosis
- little lymphoid infiltrate
- Variable associated fibrosis
What causes sarcoidosis?
Unknown causes - idiopathic
Sarcidosis mainly affects what demographic?
Young adults
Afro-americans seem abnormally at risk
F>M
What is the prevalence of sarcoidosis?
3-4/100000 in the uk
20/100000 afro-americans in USA
Less common in equatorial regions - disease of temperate climates
Sarcoidosis is multisystemic
What organs are most commonly involved?
Lymph nodes - almost 100% Lungs - >90% Spleen - 75% Liver - 70% Skin, eyes, skeletal muscle - 50% Bone marrow - 20% Salivary glands - up to 50%
What is the typical clinical presentation of sarcoidosis?
Young adult with:
- Acute athralgia (joint pain)
- Erythema nodosum (inflammation of fat cells)
- Bilateral hilar lymphadenopathy
Can be patient with SOB, cough and abnormal CXR
Or sub-clinical with abnormal CXR
What is the main treatment medication for sarcoidosis?
Corticosteroids
What is used to diagnose sarcoidosis?
Clinical findings/history
Imaging findings
Serum levels of Ca2+ and ACE
Biopsy findings
What type of hypersensitivity is associated with sarcoidosis and why?
Type 4
Type 4 hypersensitivity related to granulomatous inflammation
