extrinsic allergic alveolitis Flashcards
define extrinsic allergic alveolitis
• Condition caused by hypersensitivity induced lung damage due to a variety of inhaled particles. It is caused by immune complex mediated tissue damage hypersensitivity (type III) and delayed hypersensitivity (Type IV).
another name for this condition?
hypersensitivity pneumonitis
what are the causes of extrinsic allergic alveolitis ?
• Inhalation of antigenic dusts induce a hypersensitivity
eg.
o Famer’s Lung - caused by spores of Saccharopolyspora.
o Pigeon Fancier’s Lung - caused by avian proteins from bird droppings
what is the epidemiology of extrinsic allergic alveolitis?
- UNCOMMON
- 2% of occupational lung disease
- 50% of reported cases affect farm workers
what are the presenting symptoms of extrinsic allergic alveolitis?
can present acutely or chronically • ACUTE o Present 4-8 hrs after exposure o REVERSIBLE episodes of: • Dry cough • Dyspnoea • Malaise • Fever • Myalgia • CHRONIC o Occurs weeks to months after exposure o Lethargy o Productive cough. o Slowly increasing breathlessness o Decreased exercise tolerance o Weight loss and anorexia
signs of acute and chronic extrinsic allergic alveolitis on examination?
• ACUTE o Rapid shallow breathing o Pyrexia o Inspiratory crepitations • CHRONIC o Fine inspiratory crepitations o Clubbing (rare)
what are the investigations for extrinsic allergic alveolitis?
• Bloods o FBC - neutrophilia, lymphopenia o NO eosinophilia o ABG - reduced PO2 + PCO2 • Serology o Test for IgG to fungal or avian antigens
what might be seen on the chest X-ray?
o Fibrosis in upper/ middle zones
what might be seen on a CT?
o Detects early changes
o May show patchy ‘ground glass’ shadowing
what might a pulmonary function test show?
result in compliance with
o Restrictive defect (low FEV1, low FVC)
what might a bronchoalveolar lavage show>?
o Increased cellularity
o Lung biopsy can also be performed
