Expansion
Organic dust exposure causing an immune reaction in the alveoli
Expansion
Named causes, each with its antigen
- Farmer’s lung - thermophilic actinomycetes in mouldy hay
- Bird fancier’s lung - avian proteins in droppings and feathers. The commonest in the UK
- Malt worker’s lung - Aspergillus clavatus
- Mushroom worker’s lung - thermophilic actinomycetes
- Cheese washer’s lung - Penicillium
- Hot tub lung - Mycobacterium avium complex
- Humidifier fever - contaminated air conditioning
Presentation
- Acute: fever, dry cough, breathlessness and myalgia 4 to 8 hours after exposure, resolving within a day or two away from it
- Chronic: progressive breathlessness, weight loss and upper zone fibrosis
“It gets better at the weekend” is the history that gives it away, as with occupational asthma.
Mechanism is mainly type III (immune complex) in the acute phase with a type IV cell mediated component in the chronic phase, so it is not IgE mediated and there is usually no eosinophilia and no atopy.
Investigations: upper zone ground glass and nodules on CT, restrictive spirometry with a reduced transfer factor, lymphocytosis on bronchoalveolar lavage, and serum precipitins showing exposure rather than disease.
Management is antigen avoidance, with steroids for acute severe episodes.