Hypersensitivity Pneumonitis
What is the key distinguishing morphological feature between hypersensitivity pneumonitis and asthma? → Hypersensitivity pneumonitis primarily affects the alveoli, while asthma involves bronchial injury.
Hypersensitivity Pneumonitis
- An immunologically mediated inflammatory lung disease primarily affecting the alveoli, also known as allergic alveolitis .
- Usually occupational, triggered by heightened sensitivity to inhaled antigens such as moldy hay, contaminated water, bird feathers, or isocyanates.
- Unlike asthma (which affects the bronchi), damage occurs at the alveolar level , manifesting as restrictive lung disease with decreased diffusion capacity, compliance, and total lung volume.
- Evidence of Immunologic Mediation:
- Bronchoalveolar lavage (BAL) reveals increased CD4+ and CD8+ T lymphocytes.
Read this in Lung Pathology — Must-Know
What our notes say
- What is the key distinguishing morphological feature between hypersensitivity pneumonitis and asthma? → Hypersensitivity pneumonitis primarily affects the alveoli, while asthma involves bronchial injury. (Respiratory Pathology 1b)
- | Known cause | Occupational (silica, asbestos, coal), drugs (amiodarone, methotrexate, nitrofurantoin, bleomycin), radiation, hypersensitivity pneumonitis (farmer's lung, bird fancier's lung) | (Interstitial Lung Diseases)
- Hypersensitivity pneumonitis: immune reaction to inhaled organic antigens (mouldy hay: farmer's lung; birds: bird fancier's lung); acute (flu-like 4–8 hours after exposure) or chronic fibrosis. (Interstitial Lung Diseases)
- Hypersensitivity pneumonitis: immune reaction to organic dusts (see also the ILD note). (Occupational Lung Disease)
- A history of bird or mould exposure would raise hypersensitivity pneumonitis, which should be excluded. (Respiratory Medicine Question Bank: 15 Clinical MCQs)
- *Classic "farmer's lung" — hypersensitivity pneumonitis from inhaled organic antigens (thermophilic actinomycetes) in mouldy hay.* (End Sem Cat: Respiratory Pathology: Emphysema, ARDS, Pneumoconiosis)
Study material on Hypersensitivity Pneumonitis
- Respiratory Pathology 1b
- End Sem Cat: Respiratory Pathology: Emphysema, ARDS, Pneumoconiosis
- Interstitial Lung Diseases
- Lung Pathology — Must-Know
- Respiratory Pathology 1b
- Respiratory Pathology 1b