What Is Alpha-1 Antitrypsin Deficiency?

Alpha-1 antitrypsin (an-tee-TRIP-sin) deficiency, or AAT deficiency, is a condition that raises your risk for certain types of lung disease, especially if you smoke. AAT deficiency is an inherited condition. "Inherited" means it's passed in the genes from parents to children.

Some people who have severe AAT deficiency develop emphysema (em-fi-SE-ma)—often when they're only in their forties or fifties. Emphysema is a serious lung disease in which damage to the airways makes it hard to breathe.

A smaller number of people who have AAT deficiency have cirrhosis (sir-RO-sis) and other serious liver diseases.

Cirrhosis is a disease in which the liver is scarred. This prevents the liver from working properly. In people who have AAT deficiency, cirrhosis and other liver diseases usually occur in infancy and early childhood.

A very small number of people who have AAT deficiency have a rare type of skin disease called necrotizing panniculitis (pa-NIK-yu-LI-tis). This skin disease can cause painful lumps under or on the surface of the skin.

This article will focus on AAT deficiency as it relates to lung disease.

Overview

Alpha-1 antitrypsin, also called AAT, is a protein made in the liver. Normally, the protein goes into the bloodstream and helps protect the body's organs from the harmful effects of other proteins. One of the main organs it protects is the lungs.

AAT deficiency occurs when the AAT proteins made in the liver aren't the right shape. They get stuck inside liver cells and can't get into the bloodstream. Because not enough AAT protein travels to the lungs to protect them, the risk of lung disease increases. Also, because too many AAT proteins are stuck in the liver, liver disease can develop.

AAT deficiency is considered severe when blood levels of the AAT protein fall below the lowest amount needed to protect the lungs.

AAT deficiency is an inherited condition caused by altered genes. It's not known how many people have it. Many people who have it may not know they have it. Estimates of how many people have the condition range from about 1 in every 1,600 people to about 1 in every 5,000 people.

Outlook

You may not have any serious complications if you have AAT deficiency, and you may live a normal lifespan. Many nonsmokers who have AAT deficiency don't develop any serious related lung diseases.

Among people with AAT deficiency who do have a related lung or liver disease, about 3 percent die each year. Smoking is the leading risk factor for life-threatening lung disease if you have AAT deficiency. If you have severe AAT deficiency, smoking can shorten your life by as much as 20 years.

AAT deficiency has no cure, but there are treatments. In most cases, treatment is based on the type of disease you develop.

November 2007