Learn About Alpha-1 Antitrypsin Deficiency

Key Facts

  • Alpha-1-antitrypsin (AAT) is a protein produced in the liver that protects the body's tissues from being damaged by infection-fighting agents released by its immune system.
  • In alpha-1 antitrypsin deficiency, the body’s normal production of AAT 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.
  • It is estimated that there are between 80,000 to 100,000 individuals affected by AAT deficiency in the United States.

How AAT Deficiency Affects Your Body

When AAT levels are reduced or absent, the balance between AAT and the enzyme elastase is thrown off and can cause damage. Normally, this enzyme plays an important role in fighting infection, but too much of it can harm healthy tissue. It causes damage to the lining and alveoli of the lung, resulting in emphysema, or permanent enlargement of the lung’s airways. This can cause problems with the exchange of gas and clearance of mucus from the lung. Additionally, AAT deficiency can affect the liver, leading to poor function and increasing the risk of cirrhosis and liver cancer. In the first three decades of life, liver disease is more common than lung disease for a person with AAT deficiency. In some individuals, AAT deficiency may cause frequent red, painful nodules on the skin.

What Causes AAT Deficiency?

AAT deficiency is an inherited condition. AAT deficiency happens when one or both parents pass on to their children an abnormal version of a gene that regulates the production of the AAT protein. Depending on the condition of the inherited genes, a person’s AAT levels may be normal, reduced or absent. When a person inherits an abnormal gene from each parent, it increases the severity of disease.

Not every individual with AAT deficiency develops emphysema, a type of COPD. People with AAT deficiency are at an increased risk of developing lung disease early in life if they smoke, 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.

Reviewed and approved by the American Lung Association Scientific and Medical Editorial Review Panel.

Page last updated: November 17, 2022

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