Lungnet

What is Alpha-1 Antitrypsin (AAT)?

AAT is a substance present normally in the blood of all people and is essential for health. It is a protein that is made in the liver and released into the bloodstream. From the bloodstream, AAT moves into the lungs where its work begins.

What does AAT do?

The main role of AAT is to protect the lungs from damage. Over the course of a lifetime, the delicate tissues of the lungs are exposed daily to a variety of inhaled materials such as pollutants, germs, dust and cigarette smoke. One aspect of the body's response as it attempts to rid the lungs of these materials is the release of enzymes by the body's cells, aimed at digesting and clearing away the harmful material. The job of AAT, an anti enzyme, is to contain and neutralise these enzymes before the enzymes digest the lung tissue itself.

What is AAT deficiency?

An estimated 1 in 2,500 Australians inherit a genetic disorder in which the liver makes and releases too little AAT into the blood. As a result, the level of AAT in the lungs is too low to protect against enzyme damage. The very thin-walled air sacs in the lungs (the alveoli) are the most vulnerable. Over the years, the alveoli are digested away more quickly than normal, often causing emphysema by age 40 to 50. The age that symptoms become noticeable can vary widely, and is heavily influenced by environmental factors, e.g. smoking or polluted environments, working in conjunction with biology.

What is emphysema?

Emphysema is an irreversible condition that results from destruction of the air sacs in the lungs. These air sacs are designed to transfer oxygen into the blood stream from the fresh air we inhale. If the air sacs are destroyed, this transfer of oxygen is reduced and breathlessness results. Cigarette smoking is the cause of most cases of emphysema. AAT deficiency is rare and is the cause of emphysema in only about 2% of cases. However, smoking severely worsens the emphysema caused by AAT deficiency.

How will emphysema affect me?

The most common symptom in emphysema is breathlessness which gets worse as the emphysema progresses.

Can I have AAT deficiency and not get emphysema?

Yes, different people have different amounts of AAT in their blood. Not all people will develop emphysema. The amount of AAT present in many cases will be enough to protect the lung against destruction. Many people with AAT levels less than 30% of normal will develop emphysema at some point during their lives. Levels above 30% of normal seem to give adequate protection unless the person is a heavy smoker or exposed to other detrimental environmental factors.

Can I relieve the symptoms of my emphysema?

Some patients find that the use of inhaled bronchodilators (e.g. Atrovent^TM, Bricanyl^TM, Ventolin^TM) help relieve their symptoms, especially the breathlessness. You should discuss this with your doctor. It is important to avoid prolonged exposure to dust, fumes and especially cigarette smoke. These pollutants can cause acceleration in the rate at which lung tissue is destroyed.

Amounts and type of AAT in your body

The exact type and concentration of AAT in your blood is determined by genetic messages called phenotypes. Many different phenotypes have been described in humans, but only a few cause significant AAT deficiency. The more common examples include:

The ZZ phenotype, which is rare, is the phenotype usually associated with emphysema.

How did I inherit this deficiency?

Each parent passes one of two possible AAT genes to
their child. If one of your parents had normal levels of AAT (i.e. phenotype MM), and the other had very low levels (i.e. phenotype ZZ), then your phenotype would be MZ (an M from one parent, and a Z from the other). In this case, you are considered to be a carrier of a defective AAT gene but your body would produce enough AAT to protect your lungs. If both parents have a MM phenotype, then you would be MM also. If both parents have a ZZ phenotype, then you would be ZZ also.

Can I be treated for AAT deficiency?

Currently, there is no cure for AAT deficiency, and there is no specific treatment for the condition in Australia. Some drugs such as bronchodilators may be helpful in managing symptoms. These should only be used on your doctor's advice.

In the future, intravenous infusions of AAT concentrate may be available to some patients. This process aims to yield higher blood concentrations of AAT, leading to improved lung protection. Although available in some parts of the world, e.g. the US and Europe, the treatment is not presently available in Australia. The treatment is yet to be proven effective, however, at time of printing clinical trials are underway.

Useful website

www.alpha1.org.au

This brochure is one in a series produced by The Australian Lung Foundation to provide information on lung disease, its treatment and related issues.

The information published by The ALF is designed to be used as a guide only, is not intended or implied to be a substitute for professional medical treatment and is presented for the sole purpose of disseminating information to reduce lung disease.

Please consult your family doctor or specialist respiratory physician if you have further questions relating to the information contained in this leaflet.

Content updated May 2008