• "Obstruction" caused by lack of elastic recoil
• Most commonly caused by smoking: produces a combination of emphysema and chronic inflammation (α-1-antitrypsin deficiency produces almost pure emphysema)
• Most likely pathogenesis involves increased protease or decreased anti-protease activity

CENTROACINAR (CENTRILOBAR) EMPHYSEMA

• Affects central (proximal) parts of the acini (respiratory bronchioles) but spares the distal alveoli
• More severe in upper lobes, esp. apical segments
• Seen in smoking and secondary to coal dust

PANACINAR (PANLOBAR) EMPHYSEMA

• Uniform enlargement of all acini in a lobule; affects all of the structures, from the respiratory bronchiole to the alveoli (the prefix pan refers to the entire acinus but not to the entire lung)
• May not necessarily involve entire lung; predominantly lower lobes and in the anterior margins of the lung
• α-1-antitrypsin deficiency is prototype