- This is also known as hypersensitivity pneumonitis and is a widespread inflammatory reaction.
- It results from repeated exposure to antigens to which the individual has already been sensitised. Examples of these antigens include:
- Mouldy hay (Farmer’s lung)
- Bird Faeces (bird fancier/pigeon fancier’s lung)
- Cotton fibres (bysinossis)
- Sugar cane fibres (bagassosis)
- Lymphocytes and macrophages infiltrate the small airways after antigen exposure.
- This either resolves or leads to pulmonary fibrosis.
- Acute:
- Follows exposure to large amounts of antigen
- sudden onset of dyspnoea, fever, chills;
- symptoms subside following cessation of exposure
- reappear on reexposure.
- Chronic:
- Results from prolonged exposure to small amounts of antigen
- insidious onset of dyspnoea, dry cough, fatigue; reticulonodular infiltrates on CXR; can progress to irreversible lung damage if exposure persists
- Lung Function tests show a reversible restrictive pattern.
- CXR can show upper zone fibrosis and/or honeycomb lung.
- Management is to remove the source of the allergen primarily.
- Acutely the patient should be given
- Oxygen
- Hydrocortisone 200mg IV
- oral prednisolone 40mg (reducing dose).
- Long term steroids can improve the outcome for patients with chronic symptoms.
Related