Low AAT serum levels can lead to Alpha1-antitrypsin deficiency (AATD) (OMIM #613490; https://www.ncbi.nlm.nih.gov/omim/; accessed on 3 August 2022), a disorder caused by variations in the SERPINA1 gene, inherited in an autosomal recessive pattern with co-dominant expression of alleles. Here, SERPINA1 is linked to alpha 1-antitrypsin deficiency.