SERPINA1 and phenylketonuria: Heterozygote carriers for recessive Mendelian (monogenic) disorders such as cystic fibrosis (MIM: 219700), medium-chain-acyl-Co-A-dehydrogenase deficiency (MIM: 201450), phenylketonuria (MIM: 261600) and alpha 1-antitrypsin (AAT) deficiency (MIM: 613490) are relatively common in the UK population (1.5% (ACADM) to ∼10% (protease inhibitor (PI)-MS)).