Pulmonary emphysema: classification, etiology, pathogenesis. Chronic obstructive diffuse emphysema
Emphysema is the abnormal enlargement of the air spaces distal to the terminal bronchiole due to the destruction of alveolar walls, without fibrosis. Emphysema is most commonly associated with smoking,
and very often occurs with chronic bronchitis, the combination of the two diseases being Chronic Obstructive Pulmonary Disease (COPD).
Classification is based on anatomic distribution within the lobule:
- Centriacinar (centrilobular) emphysema
- Central or proximal parts of acini are affected, while distal ones are spared
- Panacinar (panlobular) emphysema
- Acini are uniformly enlarged, affecting all of the alveoli
- Distal acinar (paraseptal) emphysema
- The proximal parts of the acini are normal, while the distal part is involved
- Irregular emphysema
- Irregular pattern of acinar damage
Gross: centriacinar (centrilobular) emphysema in a smoker. Small holes lined by black anthracotic pigment sit at the centre of each lobule, with preserved lung around them (ruler in cm).
Image: “Centrilobular emphysema 865 lores” by Dr. Edwin P. Ewing, Jr., Public domain, via Wikimedia Commons.
Remember: each type has its typical patient and site:
- Centriacinar: heavy smokers, worst in the upper lobes and apical segments (over 95% of clinical cases)
- Panacinar: α1-antitrypsin deficiency, worst in the lower lobes
- Paraseptal: next to the pleura and septa; ruptured subpleural cysts cause spontaneous pneumothorax in young adults
Etiology and pathogenesis
- Exposure to toxic substances are inhaled, and induce ongoing inflammation with accumulation of neutrophils, macrophages and lymphocytes in the lung
- elastases, cytokines and oxidants are released causing epithelial injury and proteolysis of the ECM
- Elastin degradation products further increase inflammation
- A genetic loss of alpha 1-antitrypsin exacerbated the issue
Diagnosis and classification is based on macroscopic appearance of lung, with diagnosis under the microscope of alveolar destruction without fibrosis leading to enlarged air spaces. The loss of elastic tissue in the alveoli means their air cannot be properly expelled from alveoli, this makes it an obstructive disease.
GP NOTEBOOK SAYS
- Treatment is the same as COPD above