Causes of emphysema - it's not just the act of smoking, it also involves genetics

According to American Lung Association, "Years of exposure to the irritation of cigarette smoke usually precede the development of emphysema."
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"Alpha1 antitrypsin deficiency-related (AAT) emphysema is caused by the inherited deficiency of a protein called alpha1-antitrypsin (AAT) or alpha1-protease inhibitor. AAT, produced by the liver, is a "lung protector." In the absence of AAT, emphysema is almost inevitable. It is responsible for 5% or less of the emphysema in the United States. People can also carry a single deficient gene that causes Alpha-1 and may pass the gene onto their children."

Smoking significantly increases the severity of the disease.