Alpha-1-antitrypsin inhibits a number of lysosomal proteases and prevents the destructive effect of elastases. If the protein is deficient, the unopposed elastases predispose to panlobular emphysema. The average age of onset is younger than in centrilobular emphysema, and the onset is also earlier in smokers than in non-smokers (cigarette smoke alters the alpha-1 antitrypsin protein).

Typically, emphysematous changes are seen in all lung zones, but with lower lobe predominance. Bronchial wall thickening, dilatation and bronchiectasis can also be seen. Bullous formation in panacinar emphysema is relatively uncommon.

The differential diagnosis to consider in emphysema are honeycombing of fibrosis, pneumatocoeles eg in PCP, cystic lung disease and bronchiolitis obliterans.