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Learn About Alpha-1 Antitrypsin Deficiency

Alpha-1 antitrypsin (AAT) deficiency is a rare genetic disorder that is passed on in families and affects the lungs, liver and skin. When this condition affects the lungs, it causes COPD (chronic obstructive pulmonary disease).

Key Facts

  • Alpha-1-antitrypsin (AAT) is a protein produced in the liver that protects the body's own tissues from being damaged by infection-fighting agents released by its immune system.
  • In alpha-1 antitrypsin deficiency, AAT production is reduced, resulting in the destruction of sensitive lung tissue.
  • AAT deficiency is inherited. The severity of disease depends in part on the abnormalities present in the genes inherited from each parent.
  • There is no cure, but treatment can help people with AAT deficiency manage their symptoms and live a better life.

What Is AAT Deficiency?

Alpha-1-antitrypsin (AAT) is a protein produced in the liver that protects the body’s own tissues from being damaged by infection-fighting agents released by its immune system. In alpha-1 antitrypsin deficiency, AAT production is reduced, allowing the body’s infection-fighting agents to damage the lining and alveoli of the lung, resulting in COPD. Additionally, AAT deficiency can also affect the liver, leading to poor function and increasing the risk of cirrhosis and liver cancer.

What Causes AAT Deficiency?

AAT deficiency is a hereditary (or inherited) condition. AAT deficiency happens when one or both parents pass an abnormal gene to their child. Based on inherited genes, AAT levels may be normal, reduced or absent. When a child inherits an abnormal gene from each parent, it increases the severity of disease.

Not every individual with AAT deficiency develops COPD. People with AAT deficiency who smoke cigarettes or are exposed to secondhand smoke, work or live in a dusty environment, have a family history of emphysema, have a personal history of asthma, or a history of repeated lung infections, are at an increased risk of developing lung disease early in life.

    This content was developed in partnership with the CHEST Foundation, the philanthropic arm of the American College of Chest Physicians.


    Reviewed and approved by the American Lung Association Scientific and Medical Editorial Review Panel. Last reviewed August 4, 2016.

    Page Last Updated: July 23, 2019

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