Extrinsic Allergic Alveolitis (Hypersensitivity Pneumonitis) Flashcards
what is EAA?
widespread diffuse inflammatory reaction in the small airways and alveoli due to inhalation of foreign antigens, usually from animals
who has a decreased risk?
smokers
what type of hypersensitivity reaction is acute hypersensitivity pneumonitis?
Type 3 (immune complex deposition) to lymphocytic alveolitis
what is the Aetiology?
- Thermophilic actinomycetes hypersensitivity reaction
- farmer’s lung - caused by mouldy hay
- Malt workers lung - whiskey industry
- Bird Fancier’s lung - Avian antigens
- Mushroom farm workers and drugs - gold bleomycin, sulphasalazine
what are the symptoms of acute EAA?
- cough
- breathlessness
- fever
- myalgia
- classically symptoms occur several hours after exposure (flu-like illness signs)
what are the signs of EAA?
- with or without pyrexia
- crackles (no wheeze)
- hypoxia
what would a CXR show?
widespread pulmonary infiltrates
how is ACUTE EAA treated?
oxygen, steroid and antigen avoidance
what are the symptoms of chronic EAA?
progressive breathlessness and cough
what are the signs of chronic EAA?
may have crackles
clubbing is unusual
what would a CXR show for chronic EAA?
shows pulmonary fibrosis - most commonly in the upper zones
what would a pulmonary function test show for chronic EAA?
show restrictive defect
- low gas transfer
how is a diagnosis for chronic EAA made?
History of exposure, precipitins (IgG antibodies to guilty antigen)
- lung biopsy if in doubt
what is the treatment for chronic EAA?
- remove antigen exposure
- oral steroids if breathless (prednisolone) or low gas transfer
what type of hypersensitivity reaction is chronic hypersensitivity pneumonitis?
type 4
