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CR - Interstitial Lung Disease (Pul Fibrosis) (i) (Aetiology (occupational…
CR - Interstitial Lung Disease (Pul Fibrosis) (i)
intro
multitude of diseases that cause fibrosis of lung parenchyma (functional tissue involved in gas transfer) / alveolar interstitium
restrictive defect
alveolar walls become fibrotic + scarred
impaired diffusion of O2+CO2
hypoxaemia + dyspnoea
Aetiology
occupational lung diseases (environmental)
pneumoconiosis (e.g. CWP)
due to inhalation of organic/inorganic dusts - air contaminants
hypersensitivity pneumonitis (aka EAA - extrinsic allergic alveolitis)
inorganic = mineral dusts - asbestosis, silicosis, berylliosis, coal
organic = aspergillus spores in hay, bird faeces, cotton fibres
also cause rhinitis, laryngitis, tracheitis, bronchitis, bronchiolitis, asthma, COPD, cancer
harmfulness of dusts depends on...
chemical composition
solubility
duration of exposure
conc
particle reactivity
coexistence of other lung diseases
size
1-5 micrometres = most dangerous - reach alveoli
over 5 ulikely to reach alveoli
<0.5 tend to act like gases + diffuse out of alveoli without causing damage
shape
long + thin (asbestos) are most dangerous
coal mining
simple CWP
complicated CWP = PMF (progressive massive fibrosis)
Caplan syndrome = PMF + RA
silica from sand, stones, quarries + ceramics
acute/chronic silicosis
PMF
Caplan syndrome
asbestos from mining, installing/removing insulation, making ores/building materials
asbestosis (diffuse fibrosis)
Caplan syndrome
pleural effusions
plaques (most common)
mesothelioma (malignant tumour around pleura - encases lung)
lung carcinoma
beryllium from working in nuclear or aircraft industries
acute berylliosis
beryllium granulomatosis
connective tissue (collagen vasc) disorders
must rule out
RA
SLE
scleroderma (thickened skin collagen, esp in hands)
dermatomyositis (rash + muscle weakness)
idiopathic
IPF (unknown aetiology)
sarcoidosis
Langerhan's cell histiocytosis
drugs: radiotx (for structures also in mediastinum e.g. breast, oesophagus), chemotx (e.g. bleomycin), amioderone (antiarrythmatic)
post-infection (TB)
interstitial space
loose connective tissue throughout lung
alveolar walls + septae
3 subdivisions
bronchovasc area
surrounds bronchi, arts + veins from root of lung to resp bronchioles
parenchymal
between alv + capill basement membrane
subpleural
beneath pleura + interloper space
Dx
CPC
MDM
difficult to Dx + Tx
interstitium not normally visible radiographically, only in disease
expanded (poor gas exchange) + attenuated (weakened)
hallmark = fibrosis + scarring
Methods of Classification
aetiology (helps with Tx)
radiology (zones of fibrosis)
upper
sarcoidosis
CWP
ankylosing spondylitis
radiation
silicosis
mid
TB
chronic EAA
lower
RA
asbestosis
IPF
drugs
scleroderma
collagen vasc diseases
widespread
different dDx per zone
histology