Alpha1 antitrypsin (α1 AT) deficiency is the only known genetic abnormality that leads to COPD; it accounts for less than 1% of COPD in the United States.
Typically:
WHY? Unimpeded neutrophil elastase contributes to the alveolar destruction of emphysema.
NAMING (disease is inherited co-dominant)
Pi*MM– Normal
Pi*S (essentially normal; leading to a mild decrease in circulating A1-PI)
Pi*null– They do NOT make any alpha-1 antitrypsin. The rare null variants that are characterized by complete absence of AAT synthesis; does not cause liver disease.
Pi*MZ– heterozygous. Heterozygotes are not deemed to be at significant risk of developing emphysema.
PI*ZZ– Homozygotes for the severe deficiency allele Z. Most* but not all severely deficient individuals develop emphysema, risk for which is markedly increased by smoking. For liver disease, the lifetime risk is estimated to be approximately 40%.
*More than 95% of persons in the severely deficient category are homozygous for the Z allele, designated PiZZ.
REFERENCES
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