Emphysema
- Lesion
Emphysema is permanent enlargement of the airspaces beyond the terminal bronchiole, with destroyed alveolar walls, mostly from smoking.
What it is
Emphysema is irreversible dilation of the airspaces distal to the terminal bronchiole with destruction of their walls and no obvious fibrosis. It is named by which part of the acinus is hit. Smokers get centriacinar emphysema in the upper lobes; α1-antitrypsin deficiency gives panacinar emphysema at the bases. Elastase from neutrophils, unchecked by antiproteases, digests the elastic walls.
Structure
- Gross: large, pale, voluminous lungs that cover the heart and flatten the diaphragm; enlarged airspaces visible on the cut surface; apical blebs or bullae in advanced disease.
- Microscopy: abnormally large alveoli separated by thin septa; septa that end in club-shaped stumps floating in the spaces; enlarged pores of Kohn.
- Loss of alveolar attachments to the outer wall of small airways; fewer capillaries.
- Small-airway inflammation and fibrosis and pulmonary arterial changes of hypoxic hypertension are often superimposed.
Step by step
- Tobacco smoke and other particles injure the epithelium and activate macrophages.
- Macrophages and epithelium release chemoattractants (leukotriene B4, IL-8, TNF); neutrophils pour in.
- Neutrophils and macrophages release elastase and other proteases that digest elastin and matrix.
- Oxidants in smoke inactivate α1-antitrypsin and add direct damage; weak NRF2 antioxidant responses worsen it.
- In PiZZ deficiency there is too little α1-antitrypsin to restrain neutrophil elastase, so destruction is diffuse and early.
- Lost elastic recoil and radial traction let bronchioles collapse in expiration: air trapping and hyperinflation.
- Infections do not start the disease but cause exacerbations.
The four patterns of emphysema
| Pattern | Part of acinus | Where in the lung | Main association |
|---|---|---|---|
| Centriacinar | Respiratory bronchiole (central) | Upper lobes, apical segments | Cigarette smoking |
| Panacinar | Whole acinus evenly | Lower lobes, bases, anterior margins | α1-antitrypsin deficiency |
| Distal acinar (paraseptal) | Alveolar ducts and sacs (distal) | Subpleural, along septa, upper half | Spontaneous pneumothorax in young adults |
| Irregular | Irregular | Around scars | Old inflammation, usually silent |
Markers
- PiZZ genotype
- PAS-positive globules in hepatocytes (α1-antitrypsin deficiency)
Clinical notes
- Pink puffer pattern: thin, barrel chest, prolonged expiration through pursed lips, little cough, low DLCO, relatively normal gases at rest.
- Panacinar emphysema in a young non-smoker or with liver disease suggests α1-antitrypsin deficiency.
- Ruptured subpleural blebs cause pneumothorax; advanced disease leads to pulmonary hypertension and respiratory failure.
Test yourself
Think of the answer, then tap the question to see it.
Which emphysema pattern is typical of smokers and where is it worst?
Centriacinar emphysema, worst in the upper lobes and apical segments.
Why does α1-antitrypsin deficiency cause emphysema?
α1-antitrypsin is the main inhibitor of neutrophil elastase; without it elastase digests the elastic alveolar walls, giving panacinar emphysema at the bases.
Why do airways obstruct in emphysema if the bronchi themselves are not blocked?
Destroyed alveolar walls no longer pull small airways open, so they collapse during expiration and trap air.
Which pattern underlies many spontaneous pneumothoraces in young adults?
Distal acinar (paraseptal) emphysema, with subpleural blebs that rupture.
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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Emphysema (MedlinePlus, US National Library of Medicine, 2025); Alpha-1 antitrypsin deficiency: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2025).
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Representative model, for educational purposes only.