Extrinsic Allergic Alveolitis (EAA) / Hypersensitivity pneumonitis
- Widespread diffuse inflammatory reaction in small airways of lung and alveoli in response to ORGANIC dusts.
- A restrictive lung disease
- P/c: fever, malaise, cough, SOB, tachypnoea, course end-inspiratory crackles, wheeze (due to allergic component of reaction).
- Chest xray
- o Fluffy nodular shadowing with subsequent development of streaky shadows particularly in upper lobes.
- Lung function tests
- o Restrictive ventilatory defect (=RLD) with a decrease in carbon monoxide gas transfer (=reduced diffusing capacity of lung).
- Polymorphonuclear leukocyte count
- o Raised immune cells due to acute inflammatory/hypersensitivity reaction
- Precipitating antibodies
- o Precipitating Abs in response the Ags present in the serum.
- o ¼ of pigeon fanciers have precipitating IgG antibodies against pigeon proteins and droppings in their serum.
- Bronchoalveolar lavage
- o Increased T lymphocytes and granulocytes (neutrophilia).
- Microbial spores contaminating vegetable matter, often acquired by inhalation:
|Disease||Situation||Antigens (mostly fungal)|
|Farmers lung||Forking mouldy hay or any other mouldy vegetable material||Thermophilic actinomycetes eg: Micropolyspora faeni|
|Bird fanciers lung||Handling pigeons, cleaning lofts or budgerigar cages||Proteins present in the bloom on the feathers and in excreta|
|Maltworkers lung||Turning germinating barley||Aspergillus clavatus|
|Humidifier fever||Contaminated humidifying systems in air conditioners or humidifiers in factories.||Possibly a variety of bacteria or amoeba. Eg: Naegleria gruberi|
|Mushroom workers||Turning mushroom compost||Thermoactinomyces|
|Cheese washers lung||Mouldy cheese||Penicillin casei
|Wine makers lung||Mould on grapes||Botrytis|
- Initial infiltration of the small airways and alveolar walls with neutrophils followed by T lymphocytes and macrophages.
- Leading to development of small non-caseating granulomas.
- Comprise multinucleated giant cells.
- Allergic response to inhaled antigens involves cellular immunity and deposition of immune complexes causing foci of inflammation through the activation of complement (‘classical pathway’).
Prevention is aim.