Resources for Physicians - Genetic Facts

Updated: June 30, 2009

A1AD is inherited in an autosomal codominant manner. When both parents are heterozygotes, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being a carrier, and a 25% chance of being unaffected and not a carrier. In the rare instance in which one parent is homozygous (PI ZZ) and one parent is heterozygous, the risk for each sib to be affected is 50%.

Unless an individual with A1AD has children with a reproductive partner who is affected or a carrier, his/her offspring will be obligate heterozygotes (carriers) for the disease-causing mutation. Carrier testing is available on a clinical basis by PI typing or mutation analysis for sibs and offspring of affected individuals.

More information on the genetics of alpha-1 antitrypsin deficiency is available at GENEReviews.