Why do some individuals have AATD?
It is an inherited condition, passed on through genes from our parents. Genes are the instructions that determine how each cell in our body functions.
We all have 2 copies of the AAT gene. One copy comes from each parent. To have AATD you must inherit 2 altered copies of the gene, one altered copy from each parent. If you inherit 1 altered and 1 normal copy of the gene you are called a carrier but you are healthy and do not have AATD.
What are the different genetic types?
There are many types, or variants, of the AAT gene. M is the normal variant. The most important abnormal variants are S and Z.
- M produces normal levels of AAT
- S produces moderately low levels of AAT
- Z produces very little AAT
There are various combinations of these variants:
- MM have normal levels of AAT.
- MS and MZ (carriers) and SS have lower but sufficient levels of AAT.
- SZ individuals have AATD. There is a 60% risk of developing early onset lung disease (COPD) before age 40 and an increased risk of liver disease.
- ZZ individuals have AATD. The vast majority will develop early onset lung disease (COPD) and have increased risk of liver disease.
How common is AATD?
Approximately 1 in 3,000 people in the UK has a form of AATD.
Approximately 1 in 25 people from Northern Europe are carriers. If you are a carrier your health will not be affected.