What is alpha-1 antitrypsin deficiency (Alpha-1)?

Alpha-1 antitrypsin (AAT) is a protein made mainly by your liver, which then moves it into your bloodstream. This protein protects your lungs and other organs from the harmful effects of irritants and infections.

Alpha-1 is a rare genetic (inherited) disorder in which people have low levels of AAT in their bloodstream. This disorder can increase your risk of developing lung and liver diseases, including emphysema (damaged air sacs in the lungs) and cirrhosis (liver scarring). The low level of AAT means that lungs are not protected, and the liver is injured by the build-up of the protein there.

Alpha-1 can cause lung problems in adults and liver problems in both adults and children. Some of these conditions can be life-threatening.

How common is alpha-1 antitrypsin deficiency (Alpha-1)?

Alpha-1 is not common. Alpha-1 occurs in about one of every 3,500 people in the U.S. However, the condition is not well-recognized and is under-diagnosed. People with alpha-1 often experience long delays between their first symptom and initial diagnosis, so asking specifically whether lung or liver symptoms could be due to alpha-1 antitrypsin deficiency may prompt earlier diagnosis.

Who is affected by alpha-1 antitrypsin deficiency (Alpha-1)?

Alpha-1 occurs in males and females equally. It is most common in white people of Central or Northern European heritage.

What causes alpha-1 antitrypsin deficiency (Alpha-1)?

Mutations (changes) in the gene that produces the AAT protein cause Alpha-1. In people with the most common abnormal type of Alpha-1 (called ZZ type), AAT proteins are misshapen. These proteins can’t pass from the liver into the bloodstream, so the number of AAT proteins in the blood is low and the amount of AAT in the liver cells is increased.

When people have low AAT levels in the bloodstream, there isn’t enough AAT protein to protect the lungs and other organs from the effects of infection or irritants. Low levels of AAT can cause conditions such as emphysema and bronchitis (inflammation of the linings of the lungs). Your risk of developing lung problems with Alpha-1 increases a lot if you smoke.

Additionally, when AAT is unable to move out of the liver, it can build up and cause damage and scarring to the liver cells. This damage can lead to disorders such as cirrhosis and liver cancer.

Alpha-1 is a genetic condition, meaning a parent passes it to a child. Severe forms of the condition develop in people who get the abnormal gene from both parents. People who get an abnormal gene from just one parent are carriers, meaning they can pass the gene to their children. They also have a small risk of developing lung disease, especially if they smoke, and of liver disease.

What are the symptoms of alpha-1 antitrypsin deficiency (Alpha-1)?

Some people with Alpha-1 do not develop related diseases and have no symptoms. You might never know you have the disorder. People who have symptoms usually notice them between ages 20 and 50.

People with lung diseases caused by Alpha-1 have symptoms like those caused by chronic obstructive pulmonary disease (COPD). Shortness of breath especially with exertion, is most common. COPD is a group of lung conditions with symptoms that can include:

Some adults with Alpha-1, and about 10% of infants with Alpha-1, develop liver disease. Signs and symptoms of liver diseases caused by Alpha-1 may include:

  • Easy bruising.
  • Jaundice (yellowing of the skin and eyes).
  • Swelling in the belly or legs from fluid.
  • Vomiting blood.

Last reviewed by a Cleveland Clinic medical professional on 12/24/2019.


Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy