Alpha-1 Antitrypsin Deficiency - Causes - Causes

Alpha-1 antitrypsin (AAT) deficiency happens when you do not make enough AAT protein. The AAT protein is made in your liver. This protein enters your blood and protects your organs, including the lungs, from damage. For example, your immune system is your body’s defense against bacteria and viruses but if it is overactive, it can damage your body while fighting diseases. The AAT protein prevents you from having too much inflammation in your lungs. Without enough AAT protein, your immune system may damage your lungs and lead to lung disease.

AAT deficiency is an inherited disease. “Inherited” means it is passed from parents to children through genes . Every person inherits two AAT genes, one gene from each parent. If you inherit a mutated gene from each parent, you will have AAT deficiency.

If you inherit a mutated AAT gene from one parent and a normal AAT gene from the other parent, you are a carrier for the condition. You might have lower levels of AAT protein in your blood, but you most likely will not have AAT deficiency. However, you might develop some complications of AAT deficiency if you smoke or regularly breathe in dust and fumes. You might also pass the mutated gene to your children.

The AAT gene can have different mutations. The most common mutations that cause AAT deficiency are called PiZ and PiS. The image below shows how mutated AAT genes are passed to children.

How AAT deficiency is inherited. In this image, both parents have a normal AAT gene and a mutated AAT gene (called being a carrier). Each child has a 25% chance of inheriting two normal genes, a 50% chance of being a being carrier, and a 25% chance of inheriting two mutated AAT genes (and having AAT deficiency).
How AAT deficiency is inherited. In this image, both parents have a normal AAT gene and a mutated AAT gene (called being a carrier). Each child has a 25% chance of inheriting two normal genes, a 50% chance of being a being carrier, and a 25% chance of inheriting two mutated AAT genes (and having AAT deficiency).

Even if you inherit two mutated AAT genes, you may not have any complications. You may never even realize that you have AAT deficiency. Scientists are conducting research to find out why some people who have AAT deficiency develop complications while others do not.