Everyone has two copies of each gene. We inherit one copy from our mother and one copy from our father. Alpha-1 carriers have one copy of an Alpha-1 mutation and one copy of a normal, functional AAT gene.

About 1 in 10 to 1 in 33 people in the U.S. are thought to be Alpha-1 carriers, but most do not know it. Carriers do not usually develop signs and symptoms of Alpha-1 unless they are also exposed to environmental triggers such as smoking.

However, if a carrier has a child with another carrier, there is a chance — 1 in 4 (or 25%) — that the child will inherit both their parents' mutations. Having two mutations significantly increases the chance of developing signs and symptoms of Alpha-1.

It is difficult to know the exact number of people who are carriers of Alpha-1, or who have Alpha-1, since it is often misdiagnosed and many people who have it go untested.

If someone is a carrier or has a family member with Alpha-1, other family members are at risk for carrying the same genetic changes. Around 116 million people worldwide are Alpha-1 carriers.

Some ethnic groups have higher rates of Alpha-1 than others. To learn more about why some ethnic groups have increased risks for certain genetic mutations, read more about the Founder Effect and the Beneficial Mutation Theory.