Pathology of Interstitial Lung Disease

Question 1

describe the pulmonary interstitium

Answer 1

alveolar lining cells - type I and II

thin elastin-rich connective component containing capillary blood vessels

Question 2

describe interstitial lung disease (ILD)

Answer 2

early stage is alveolitis - injury with inflammatory cell infiltration
acute ILD is exemplified by adult respiratory distress syndrome
late stage is characterised by fibrosis
clinical effects due to hypoxia (respiratory failure, type 1) and cardiac failure

Question 3

describe causes of ILD

Answer 3

environmental - minerals, drugs, radiations, post-ARDS (hypersensitivity - mouldy hay, avian products
unknown (idiopathic) - connective tissue diseases, idiopathic pulmonary fibrosis

the diagnosis is based on clinical features often with biopsy

Question 4

describe biopsy in ILD

Answer 4

transbronchial biopsy - special forceps used at bronchoscopy
thoracoscopic biopsy - more invasive but reliable and generates far more tissue

Question 5

describe chronic ILD

Answer 5

idiopathic pulmonary fibrosis
sarcoidosis
hypersensitivity pneumonitis (extrinsic allergic alveolitis)
pneumoconiosis 
connective tissue diseases

Question 6

describe idiopathic pulmonary fibrosis

Answer 6

aka cryptogenic fibrosing alveolitis (CFA), usual interstitial pneumonia (UIP)
progressive interstitial fibrosis of unknown cause
variable associated inflammation
finger clubbing

Question 7

describe the pathology of idiopathic pulmonary fibrosis

Answer 7

sub-pleural and basal fibrosis
inflammatory component variable
terminally lung structure replaced by dilated spaces surrounded by fibrous walls
–> honeycombing

Question 8

describe hypersensitivity pneumonitis (HP)

Answer 8

chronic inflammatory disease;
small airways
interstitium
occasional granulomas

allergic origin;
type III hypersensitivity
type IV hypersensitivity

Question 9

describe causes of hypersensitivity pneumonitis

Answer 9

thermophilic bacteria - farmers lung
avian proteins - bird fanciers lung
fungi - malt workers lung

precipitins (antibodies) often detectbale in serum
unusual cases come to biospy

Question 10

describe sarcoidosis

Answer 10

multi-system granulomatous disorder of unknown cause (defined by histological means)
pulmonary involvement is common
most cases mild and self-limiting

Question 11

describe other manifestations of sarcoidosis

Answer 11

uveitis (inflammation of iris)
erythema nodosum
lymphadenopathy
hypercalcaemia

Question 12

describe pulmonary involvement in connective tissue disease

Answer 12

interstitial fibrosis (milder than IPF)
pleural effusions
rheumatoid nodules

Question 13

describe pneumoconiosis

Answer 13

lung disease caused by mineral dust exposure;
asbestosis
coal workers lung
silicosis

disease is dependant on;
particle size
reactivity of particle
clearance of particle
host response

Question 14

describe asbestos

Answer 14

straight (amphibole) fibres dangerous

causes;
parietal pleural plaques
interstitial fibrosis (asbestosis)
bronchial carcinoma 
mesothelioma