Chronic obstructive pulmonary disease is the chronic blockage of airways in the lungs, causing difficulty breathing and shortness of breath. Smoking is the leading cause of COPD. While rare, a genetic disorder known as alpha-1 antitrypsin deficiency can also cause COPD. Most people have two normal copies of the gene. If you inherit one mutated gene, you are a carrier and can generally prevent COPD by maintaining a healthy lifestyle. However, if two alpha-1 deficient genes are inherited, you will likely develop COPD, despite any lifestyle precautions.