Extrinsic Allergic Alveolitis

Question 1

What is extrinsic allergic alveolitis?

Answer 1

In sensitised individuals, repetitive inhalation of allergens provokes a hypersensitivity reaction which varies in intensity and clinical course depending on the antigen.

Acute phase - alveoli are infiltrated with acute inflammatory cells
Early diagnosis and prompt allergen removal can halt and reverse disease progression.

With chronic exposure - granola formation and obliterative bronchiolitis

Question 2

What are causes of extrinsic allergic alveolitis?

Answer 2

Bird fancier’s and pigeon fancier’s lung (proteins in bird droppings)
Farmer’s and mushroom workers lung
Malt worker’s lung

Question 3

What are acute clinical features of extrinsic allergic alveolitis?

Answer 3

4-6h post exposure

Fever, rigors, myalgia, dru cough, dyspnoea, fine bibasal crackles

Question 4

What are chronic features of extrinsic allergic alveolitis?

Answer 4

Finger clubbing
Increasing dyspnoea
Weight loss
Exersional dyspnoea
Type 1 RF
Cor pulmonale

Question 5

What tests for extrinsic allergic alveolitis?

Answer 5

Acute:
Blood: FBC (neutrophilic), Raised ESR, ABG, serum antibodies (Exposure/previous sensitisation)
CXR - upper zone mottling/consolidation
LFT: reversible restrictive defect

Chronic
Bloods: serum antibodies
CXR: upper zone fibrosis, honeycomb lung
HRCT: nodules, growing glass appearance, extensive fibrosis.
Increased lymphocytes and mast cell on bronchoalveolar lavage

Question 6

What does spirometry show?

Answer 6

Restrictive defect:
FEV1 <80%
FVC <80%
FEV1:FVC > 70%

Question 7

What does CXR show?

Answer 7

Acute: upper zone mottling/ consolidation

Chronic: upper zone fibrosis, honeycomb lung

Question 8

what is management for extrinsic allergic alveolitis? acute? Chronic?

Answer 8

Acute: remove allergen and give O2 (35-60%)
PO prednisolone, reducing course

Chronic:
Allergen avoidance, wear facemark
Long term steroids