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 variant. The condition is most common among Europeans and North Americans of European descent.

Adults with severe AAT deficiency will develop emphysema, sometimes before 40 years of age. Smoking can increase the risk for emphysema and make it occur earlier.

Symptoms may include any of the following:

• Shortness of breath with and without exertion, and other symptoms of COPD
• Symptoms of liver failure
• Loss of weight without trying
• Wheezing
• Coughing

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

• AAT blood test
• Arterial blood gases
• Chest x-ray
• CT scan of the chest
• Genetic testing
• Lung function tests

Your health care provider may suspect you of having this condition if you develop:

• COPD before age 45
• COPD but you have never smoked or been exposed to toxins
• COPD and you have a family history of the condition
• Cirrhosis and no other cause can be found
• Cirrhosis 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 or every 4 weeks. This is only slightly effective at preventing more lung damage in people without end-stage disease. This procedure is called augmentation therapy.

If you smoke, you need to quit.

Other treatments are also used for COPD and cirrhosis.

Lung transplant can be used for severe lung disease, and liver transplant can be used for severe cirrhosis.

Some people with this deficiency will not develop liver or lung disease. If you quit smoking, you can slow the progression of the lung disease.

COPD and cirrhosis can be life threatening.

Complications of AAT deficiency include:

• Bronchiectasis (damage of the large airways)
• COPD
• Liver failure or cancer

Contact your provider if you develop symptoms of AAT deficiency.

AAT deficiency; Alpha-1 protease deficiency; COPD - alpha-1 antitrypsin deficiency; Cirrhosis - alpha-1 antitrypsin deficiency

Han MK, Lazarus SC. COPD: diagnosis and management. In: Broaddus VC, Ernst JD, King TE, et al, eds. Murray and Nadel's Textbook of Respiratory Medicine. 7th ed. Philadelphia, PA: Elsevier; 2022:chap 64.

Masson VK, Boas SR. a1 -antitrypsin deficiency and emphysema. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 442.

Tejwani V, Stoller JK. The spectrum of clinical sequelae associated with alpha-1 antitrypsin deficiency. Ther Adv Chronic Dis. 2021;12_suppl. PMID: 34408829 pubmed.ncbi.nlm.nih.gov/34408829/.

Updated by: Allen J. Blaivas, DO, Division of Pulmonary, Critical Care, and Sleep Medicine, VA New Jersey Health Care System, Clinical Assistant Professor, Rutgers New Jersey Medical School, East Orange, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.