Extrinsic Allergic Alveolitis Flashcards
Define Extrinsic Allergic Alveolitis
Inflammation of the alveoli and distal bronchioles caused by an immune response to inhaled allergens
AKA hypersensitivity pneumonitis (HP)
Aetiology of Extrinsic Allergic Alveolitis
NON-IgE mediated immunological inflammation
Repetitive inhalation of allergens (Fungal spores, avian proteins) in a sensitised individual will provoke a hypersensitivity reaction
Caused by: Bird-fancier’s and pigeon-fancier’s lung Farmer’s and mushroom worker’s lungs Malt worker’s lung Sugar-worker’s lung
Risk factors for Extrinsic Allergic Alveolitis
Smoking Viral infection Nitrofurantoin, methotrexate, rituximab Herbal supplements Exposure to mould, bacterial, avian proteins
Symptoms of Extrinsic Allergic Alveolitis
4-6hrs post-exposure: Fever Rigors Myalgia Dry cough/productive cough Dyspnoea Malaise
Chronic: Increasing dyspnoea Weight loss/anorexia Exertion dyspnoea Malaise
Signs of Extrinsic Allergic Alveolitis on examination
4-6hrs post-exposure: fine bi-basal crepes
Chronic:
Clubbing (50%)
Cor pulmonale signs: Raised JVP ± prominent A wave, RHF
Type I resp. Failure
Investigations for acute Extrinsic Allergic Alveolitis
FBC: neutrophil is, leucocystosis | normocytic normochomic anaemia
ESR/CRP: raised
Serum antibodies: may indicate exposure
CXR: Upper-zone mottling/consolidation | lymphadenopathy
LFTs: Reversible restrictive defect, reduced gas transfer during acute attacks
Investigations for chronic Extrinsic Allergic Alveolitis
Serum antibodies
Albumin: reduced
CXR: often normal, may show upper-zone fibrosis
CT chest: Nodules, ground-glass appearance, extensive fibrosis, honeycomb lung
Lung function tests: Restrictive defective (Both FEV1 and FVC reduced - ratio is normal)
BAL: Increased lymphocytes and mast cells
Biopsy: Bronchocentric infiltrate consisting of lymphocytes, plasma cells, neutrophils, foamy macrophages, non-caseating granulomas, interstitial fibrosis
