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

AAT deficiency

Alpha-1 antitrypsin (AAT) is a type of protein called a "protease inhibitor." AAT normally works to protect the lungs from a naturally occuring destructive enzyme that is produced by the lungs in response to infections and toxins (such as cigarette smoke). Without enough AAT, these enzymes slowly destroy the lung tissue.

AAT deficiency is caused by a genetic defect that results in not enough AAT in the liver, lungs, and blood. Persons with this deficiency may also develop liver disease.

Studies show that AAT deficiency may be more common than once thought. Most adults with severe deficiency will develop emphysema, which often begins before age 40. Smoking can increase your risk. The condition is most common among Europeans and North Americans of European descent.

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

A physical examination may reveal a barrel-shaped chest. Listening to the chest with a stethoscope may reveal 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
• Pulmonary function test

Your doctor may suspected you having this condition if you develop:

• Emphysema before age 45
• Emphysema but have never smoked or been exposed to toxins
• Liver disease or hepatitis and no other cause can be found

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

• Cirrhosis or liver failure
• Emphysema
• Liver cancer

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

Köhnlein T, Welte T. Alpha-1 antitrypsin deficiency: pathogenesis, clinical presentation, diagnosis, and treatment. JAMA. 2008;121(1):3-9.

Stoller JK, Tomashefski J, Crystal RG, et al. Mortality in individuals with severe deficiency of alpha-1-antitrypsin: Findings from the National Heart, Lung, and Blood Institute Registry. Chest. April 2005;127:1196-1204.