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.A.D.A.M.

Causes, incidence, and risk factors

Alpha-1 antitrypsin (AAT) is a type of protein called a "protease inhibitor." It 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.

Studies show that AAT deficiency may be more common than was once thought.

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

Persons with this deficiency may also develop liver disease.

Symptoms

• Shortness of breath with and without exertion, and other symptoms of chronic obstructive pulmonary disease (COPD)
• Symptoms of severe liver disease ( cirrhosis)
• Unintentional weight loss
• Wheezing

Signs and tests

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

• Alpha-1 antitrypsin blood test
• Arterial blood gases
• Chest x-ray
• CT scan of the chest
• Genetic testing
• Lung function test

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

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

Treatment

Treatment for AAT deficiency involves replacing the missing AAT protein. The protein is given through a vein each week. However, it is not yet well known who may benefit from such therapy.

If you smoke, you need to quit.

Other treatments for emphysema and cirrhosis are also used.

Expectations (prognosis)

Some people with this deficiency will not develop liver or lung disease. However, emphysema and cirrhosis can be life threatening.

Complications

• Bronchiectasis
• Cirrhosis or liver failure
• Emphysema
• Liver cancer

Calling your health care provider

Call your health care provider if you develop symptoms of AAT deficiency.

References

1. Bacon BR. Inherited and metabolic hepatic disorders. In:Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 93.
2. Niewoehner DE. Chronic obstructive pulmonary disease. In:Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 88.
3. 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. 5th ed. Philadelphia, Pa: Saunders Elsevier; 2010:chap 39.
4. Silverman EK, Sandhaus RA. Alpha-1 antitrypsin deficiency. N Engl J Med 2009;360:2749-2757. [PubMed: 19553648]

Review Date: 8/30/2012.

Reviewed by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Denis Hadjiliadis, MD, Assistant Professor of Medicine, Division of Pulmonary, Allergy and Critical Care, University of Pennsylvania, Philadelphia, PA. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.