Emphysema, which is a form of chronic obstructive pulmonary disease, or COPD, can occur when a person inherits a defective copy of the AAT gene from both parents. People who inherit just one copy of the gene are called “carriers.” These individuals also have lower levels of AAT in the lungs, which predispose them to the risk of developing emphysema, but generally they will only develop the disease if they are also cigarette smokers or have been exposed to excessive amounts of environmental pollution. When emphysema does develop in carriers, it is also generally at an older age.

Worldwide, about 116 million people are estimated to be carriers of the defective gene that causes Alpha-1. About 100,000 people in the U.S. are believed to have inherited two copies of the gene, putting them at extreme risk for emphysema. Many, however, are either under-diagnosed or undiagnosed. About 3 percent of people with COPD may actually have undiagnosed Alpha-1 deficiency.