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Hypersensitivity Pneumonitis (Aetiology (Malt worker's lung:…
Hypersensitivity Pneumonitis
Definition
Inhalation of allergens provokes a hypersensitivity reaction
Also known as extrinsic allergic alveolitis
Pathophysiology
Chronic exposure = granuloma formation and obliterative bronchiolitis occurs
Early diagnosis and prompt allergen removal can halt and reverse disease progression
Acute phase = Alveoli are infiltrated with acute inflammatory cells
Allergens inhaled are fungal spores or avian proteins
Aetiology
Malt worker's lung: Aspergillus clavatus
Sugar worker's lung: Thermoactinomyces sacchari
Bird-fancier's lung: proteins in bird droppings
Mushroom worker's lung: Thermoactinomyces vulgaris
Farmer's lung: micropolyspora faeni
Signs
Acute
Myalgia
Dry cough
Dyspnoea
Rigors
Fever
Crackles
Chronic
Weight loss
Exertional dyspnoea
Increasing dyspnoea
Type 1 resp failure
Finger clubbing
Cor pulmonale
Investigations
Chronic
Chest X-ray: Upper zone fibrosis, honeycomb lung
Lung function tests: Restrictive defect
Bloods: serum antibodies
Bronchoalveolar lavage fluid shows increased lymphocytes and mast cells
Acute
Chest X-Ray: Upper zone mottling
Lung function tests: reversible restrictive defect
Bloods: neutrophilia, raised ESR, serum antibodies
Treatment
Acute
Give oxygen: 35-60%
Prednisolone
Remove allergen
Chronic
Long term steroids
Compensation
Remove allergen and exposure