Extrinsic allergic Alveolitis

Question 1

What is Extrinsic allergic alveolitis?

Answer 1

Hypersensitivity Pneumonitis

Interstitial inflammatory disease of the distal gas-exchanging parts of the lung caused by inhalation of organic dusts

Question 2

What is the cause for Extrisic allergic alveolitis?

Answer 2

• Antigenic organic dust contains allergens e.g. microbes (bacteria, fungi, amobae) or animal proteins
• Causing a Type 3 Hypersensitivity Reaction

Question 3

Which allergens might cause extrinsic allergic alveolitis?

Answer 3

Generally organic dusts:

• Farmer’s lung: Mouldy hay containing thermophilic actinomycetes
• Pigeon/budgerigar fancier’s lung: Bloom on bird feathers and excreta
• Mushroom worker’s lung: Compost containing thermophilic actinomycetes.
• Humidifier lung: Water-containing bacteria and Naegleria (amoeba).
• Maltworker’s lung: Barley or maltings containing Aspergillus clavatus.

Question 4

What is the epidemiology of extrinsic allergic alveolitis?

Answer 4

Uncommon

2% of occupational lung disease, 4-10/100.000/ year

Question 5

What are the risk factors for the development of extrinsic allergic alveolitis?

Answer 5

• Smoking
• Exposure to antigens
  
  • Pigeon breeder/bird
  • Farmer
  • Mould
  • Epoxy
  • Metal-working fluid
  • Certain drugs

Question 6

What are the symptoms of acute Extrinsic allergic alveolitis?

Answer 6

• Onset 4-12 hrs after exposure
• Recurrent episodes of dry cough
• Dyspnoea
• Malaise
• Fever
• Myalgia
• Bibasillar rales
• Wheeze and productive cough with high level exposures

Question 7

What are the symptoms of chronic extrinsic allergic alveolitis?

Answer 7

• Increasign Dyspnoea with decreased exercise tolerance
• Weight loss
• Normally due to chronic low level exposure

Question 8

What are signs of acute extrinsic allergic alveolitis on examination?

Answer 8

Acute

• Rapid shallow breathing,
• pyrexia,
• inspiratory crepitations
• Might devellop wheeze in high level repetitive exposure

Question 9

What are signs of chronic extrinsic allergic alveolitis?

Answer 9

• Fine inspiratory crepitations (see Cryptogenic fibrosing alveolitis).
• Finger clubbing

Question 10

What are investigations you would do in a person with Extrinsic allergic alveolitis?

Answer 10

• Blood:
  
  • FBC (neutrophilia, lymphopenia),
  • ABG (decreased PO2 and PCO2),
  • ESR (increased)
• Serology:
  
  • Precipitating IgG to fungal or avian antigens in serum (not diagnostic)
• Imaging
• Pulmonary function tests:
• Restrictive ventilatory defect
  
  • (decreased FEV1 andFVC with preserved or increased ratio),
  • decrease TLCO
• Bronchoalveolar lavage: Increased cellularity with increase CD8+ suppressor T cells.
• Lung biopsy (transbronchial or thorascopic)

Question 11

What are typical X-Ray findings of Extrinsic allergic alveolitis?

Answer 11

• CXR:
  
  • Acute:
    
    • often normal,
    • shadow ´ground glass
    • ´w. alveolar shadowing/nodular opacities in middle/lower zones
  • Chornic:
    
    • Fibroisis in upper zones
• High-resolution CT-thorax:
  
  • Patchy ‘ground glass’ shadowing and nodules.