Alpha-1-antitrypsin deficiency

What is alpha-1-antitrypsin deficiency?

Alpha-1-antitrypsin deficiency (AATD) is a rare, inherited condition, which can cause lung and liver problems. It’s thought that about 25,000 people in the UK have the genetic condition though most remain healthy so few have been diagnosed.

People with AATD lack a protective enzyme inhibitor called alpha-1-antitrypsin. This makes them much more vulnerable to the effects of inhaling smoke or other toxic materials like dust, fumes or chemicals. 

This deficiency increases the risk of lung disease. If you have AATD, you’re more likely to develop chronic obstructive pulmonary disease (COPD). You may also develop COPD at a younger age than usual and it may progress more rapidly than normal COPD, especially if you smoke.

It can also sometimes cause liver problems, skin rashes and immune problems.

What is alpha-1-antitrypsin?

Alpha-1-antitrypsin (AAT) is an enzyme inhibitor. This means it controls enzymes in your body.

What are enzymes?

Enzymes are proteins that make chemical processes happen in your body. They do lots of different jobs. For example, some are involved in building up and breaking down parts of the body. Some help digestion. Others help you move by using energy to make your muscles contract. When enzymes are not properly controlled they can cause damage to your body tissue.

AAT is mainly produced by your liver. It’s released into your blood and works in all parts of your body. It especially works in the lungs to control the enzymes that can cause lung damage.

What does alpha-1-antitrypsin do in my lungs?

When you have an infection, white blood cells in your body work to fight off the infection. As part of their defence, they produce enzymes that allow them to move into the lung and break down the bacteria causing the infection. They also do this as part of your body’s response to breathing in cigarette smoke. 

But as well as breaking down proteins in the bacteria, these enzymes can also damage the proteins which your lungs are made out of. To stop this, alpha-1-antitrypsin (AAT) damps down the effect of the enzymes, reducing the damage to the surrounding lung. 

If you have a low level of AAT, the surrounding lung isn’t protected as well as it should be. So when you breathe in smoke or have a lung infection, the enzymes will cause much more damage to the surrounding healthy lung. This can lead to the development of chronic obstructive pulmonary disease (COPD). It’s especially damaging to the small air spaces (alveoli) where oxygen and carbon dioxide are exchanged – these become bigger leaving holes referred to as emphysema.

Next: Causes of Alpha-1-antitrysin deficiency >

Download our AATD PDF (394KB)

Last medically reviewed: September 2017. Due for review: September 2020

This information uses the best available medical evidence and was produced with the support of people living with lung conditions. Find out how we produce our information. If you’d like to see our references get in touch.