Northern Genetics Service

Alpha-1 Antitrypsin Deficiency (AATD)

This leaflet is written for people diagnosed with Alpha-1 antitrypsin deficiency (AATD), or those found to be carriers of the disorder and their family members.

Alpha-1 Antitrypsin Deficiency (AATD)Show [+]Hide [-]

What is AATD?

Alpha-1 antitrypsin (AAT) is a substance made in the liver that circulates in the bloodstream.

AAT protects the body tissues against damage from chemicals made by the body in response to infection and smoking.

If you have AATD you have lower levels of AAT in your blood.

What are the effects of AATD?

The effects are varied. It affects the lungs and liver.

  • Some individuals don’t suffer any ill effects.
  • Some remain healthy until adulthood, after which breathing problems may develop due to a condition called Chronic Obstructive Pulmonary Disease (COPD). Individuals experience shortness of breath, which can progress in some cases to severe breathing difficulties

Some develop scar tissue (cirrhosis) of the liver in middle age. Occasionally newborn babies with AATD develop inflammation of the liver (hepatitis) and in a few cases the hepatitis does not improve and develops into cirrhosis in childhood.

Genetics of AATDShow [+]Hide [-]

Why do some individuals have AATD?

It is an inherited condition, passed on through genes from our parents. Genes are the instructions that determine how each cell in our body functions.

We all have 2 copies of the AAT gene. One copy comes from each parent. To have AATD you must inherit 2 altered copies of the gene, one altered copy from each parent. If you inherit 1 altered and 1 normal copy of the gene you are called a carrier but you are healthy and do not have AATD.

What are the different genetic types?

There are many types, or variants, of the AAT gene. M is the normal variant. The most important abnormal variants are S and Z. 

  • M produces normal levels of AAT
  • S produces moderately low levels of AAT
  • Z produces very little AAT

There are various combinations of these variants:

  • MM have normal levels of AAT.
  • MS and MZ (carriers) and SS have lower but sufficient levels of AAT.
  • SZ individuals have AATD. There is a 60% risk of developing early onset lung disease (COPD) before age 40 and an increased risk of liver disease.
  • ZZ individuals have AATD. The vast majority will develop early onset lung disease (COPD) and have increased risk of liver disease.

How common is AATD?

Approximately 1 in 3,000 people in the UK has a form of AATD.

Approximately 1 in 25 people from Northern Europe are carriers. If you are a carrier your health will not be affected.

AATD & healthShow [+]Hide [-]

How can those with AATD look after their health?

It is important not to smoke and avoid passive smoking. Smoking and other lung irritants such as dust and chemicals speeds up the development of the lung disease. Individuals with AATD are more likely to develop liver problems if they consume more alcohol than the recommended weekly allowance. It is therefore very important to moderate alcohol consumption.

What advice is there for carriers?

Your health is not normally affected if you are a carrier of AATD. However, it is advisable to avoid cigarette smoke, as it may be that carriers are slightly more at risk of developing lung problems if they smoke or are exposed to passive smoke.

Frequently Asked QuestionsShow [+]Hide [-]

1.    I’m a carrier, will my children have AATD?

a)   If your partner is also a carrier of AATD there will be a:

  • 1 in 4 (25%) chance the child will have AATD
  • 1 in 2 (50%) chance the child will be a carrier for AATD
  • 1 in 4 (25%) chance the child will neither be a carrier nor have AATD

 AATD fig1a

b)   If your partner is not a carrier of AATD or does not have AATD you will not have children with AATD, but each time you have a child there will be a 50% chance that they could be a carrier.

 AATD fig1b

2.   I have AATD, will my children also have the deficiency?

a)   If your partner is not a carrier, then none of your children will have AATD but all your children will be carriers.


 AATD fig2a

b)   If your partner is a carrier of AATD, there is a 50% chance of each pregnancy producing a child with AATD and a 50% chance that they will be a carrier.

AATD fig2b

Further questions?Show [+]Hide [-]

If you have any further questions please contact:


Northern Genetics Service
Institute of Genetic Medicine
The International Centre for Life
Central Parkway

Telephone:     0191 241 8600 (8.30am to 5.00pm Monday to Friday)
Fax:                0191 241 8799


Alpha-1 uk support group:

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