Extrinsic Allergic Alveolitis

Question 1

Define extrinsic allergic alveolitis

Answer 1

Interstitial inflammatory disease of the alveoli and distal bronchioles caused by inhalation of
organic dusts or animal protein

Question 2

What are some causes/risk factors of extrinsic allergic alveolitis?

Answer 2

• mouldy hay (actinomycetes) -> farmer’s lung
• bloom on feathers or excreta (animal-derived proteins) -> bird breeder’s lung
• water-containing bacteria and Naegleria (amoeba) from air conditioning (aureobastidium actinomycetes) -> air conditioner’s/humidifier’s lung
• compost (aspergillus) -> compost lung
• polyurethan foam (isocyanates) -> chemical worker’s lung

Question 3

What are the presenting symptoms of extrinsic allergic alveolitis?

Answer 3

Acute
• Dry cough
• Dyspnoea
• Malaise
• Fever
• Myalgia

Subacute
• Wheeze
• Productive cough

Chronic
• Slowly worsening SOB
• Reduced exercise tolerance
• Weight loss

Question 4

What are the signs of extrinsic allergic alveolitis?

Answer 4

Signs
Acute
• Rapid shallow breathing
• Pyrexia
• Inspiratory crepitations

Chronic
• Fine inspiratory crepitations
• Clubbing

Question 5

What are the investigations for extrinsic allergic alveolitis?

Answer 5

• immunological response to causative antigen
• FBC - leukocytosis; normocytic, normochromic anaemia
• erythrocyte sedimentation rate - elevated
• albumin - low
• CXR - infiltrates, nodular or patchy; fibrosis
• CT chest - ground-glass shadowing/attenuation and poorly defined micronodules;chronic - mosaic attenuation, centrilobular nodules, and relative basal sparing
• pulmonary function test - restrictive; mixed restrictive/obstructive
• diffusing lung capacity of CO - decreased