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Alpha-1 antitrypsin deficiency

Alpha-1 antitrypsin (AAT) deficiency is a condition in which the body does not make enough of a protein that protects the lungs and liver from damage. The condition can lead to emphysema and liver disease.


Alpha-1 antitrypsin (AAT) is a type of protein called a protease inhibitor. AAT is made in the liver and it works to protect the lungs and liver.

AAT deficiency means there is not enough of this protein in the body. It is caused by a genetic defect. The condition is most common among Europeans and North Americans of European descent.

Adults with severe AAT deficiency will develop emphysema, often before age 40. Smoking can increase the risk of emphysema. Other patients have a higher level of AAT in their blood, and therefore have a less severe condition.

Persons with this deficiency may also develop liver disease.


Symptoms may include any of the following:

Exams and Tests

A physical examination may reveal a barrel-shaped chest, wheezing, or decreased breath sounds. The following tests may also help with diagnosis:

Your doctor may suspect you of having this condition if you develop:

  • Emphysema before age 45
  • Emphysema but you have never smoked or been exposed to toxins
  • Emphysema and you have a family history of the condition
  • Liver disease and no other cause can be found
  • Liver disease and you have a family history of liver disease


Treatment for AAT deficiency involves replacing the missing AAT protein. The protein is given through a vein each week. This is only slightly effective at preventing more lung damage in patients without end-stage disease.

If you smoke, you need to quit.

Other treatments are also used for emphysema and cirrhosis.

Outlook (Prognosis)

Some people with this deficiency will not develop liver or lung disease.

Emphysema and cirrhosis can be life threatening.

Possible Complications

When to Contact a Medical Professional

Call your doctor if you develop symptoms of AAT deficiency.

Alternative Names

AAT deficiency; Alpha-1 protease deficiency


Bacon BR. Inherited and metabolic hepatic disorders. In: Goldman L, Schafer AI, eds.Goldman's Cecil Medicine

Niewoehner DE. Chronic obstructive pulmonary disease. In: Goldman L, Schafer AI, eds.Goldman's Cecil Medicine

Shapiro SD, Reilly JJ Jr, Rennard SI. Chronic bronchitis and emphysema. In: Mason RJ, Broaddus CV, Martin TR, et al.Murray & Nadel's Textbook of Respiratory Medicine

Silverman EK, Sandhaus RA. Alpha-1 antitrypsin deficiency. N Engl J Med

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Update Date 8/25/2014

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