Extrinsic allergic alveolitis

Question 1

Extrinsic allergic alveolitis?

Answer 1

Interstitial inflammatory disease of the distal gas-exchanging parts of the lung caused by inhalation of organic dusts. Also known as hypersensitivity pneumonitis. Inhalation of antigenic dusts induce a hypersensitivity response in susceptible individuals.

Question 2

What is the pulmonary interstitium?

Answer 2

Question 3

Extrinsic allergic alveolitis causes?

Answer 3

Antigenic dusts include microbes and animal proteins
Examples:

Famer’s Lung - caused by mouldy hay containing thermophilic actinomycetes

Pigeon Fancier’s Lung - caused by blood on bird feathers and excreta

Maltworker’s Lung - caused by barley or maltlings containing Aspergillus clavatus

Question 4

Extrinsic allergic alveolitis epidemiology?

Answer 4

UNCOMMON
2% of occupational lung disease
50% of reported cases affect farm workers Geographical variation

Question 5

Extrinsic allergic alveolitis acute symptoms?

Answer 5

4-12hrs after exposure, reversible episodes of dry cough, dyspnoea, malaise, fever, myalgia, wheeze

Question 6

Extrinsic allergic alveolitis chronic symptoms?

Answer 6

slowly increasing breathlessness, decreased exercise tolerance, weight loss, exposure is usually chronic, low-level and there may be no history of previous acute Episodes.

Question 7

Extrinsic allergic alveolitis signs?

Answer 7

Acute; rapid shallow breathing, pyrexia, inspiratory crepitations

Chronic; clubbing, fine inspiratory crackles.

Question 8

Extrinsic allergic alveolitis investigations?

Answer 8

FBC (neutrophilia, lymphopenia),

ABG,

serology (test for IgG to fungal antigens)

CXR (sometimes see fibrosis),

Pulmonay function tests (Restrictive defect (low FEV1, low FVC) Preserved or increased FEV1/FVC ratio Reduced total lung capacity),

Bronchoalveolar lavage.