Clearly, genetics is one of the factors that causes DAO Deficiency. In the same family unit, its members share this deficiency and many chronic pathologies that until now were considered “hereditary”.
The genetic sequence of DAO enzyme is found in a fragment which is located on chromosome 7 (7q34-q36) of the human genome and is composed of 5 exons and 4 introns.
There have been detected many differences in the sequence of exons and introns of this gene that are due to their genetic polymorphism. In total, according to data from the National Center for Biotechnology Information (NCBI), there are 85 variants of a single nucleotide polymorphisms (SNPs) located and identified in the human gene of the DAO enzyme (AOC1). 17 of these SNPs are found in the exons, of which 7 produce replacement of amino acids, being candidates for cause alterations in the metabolic capacity of the enzyme.
Of all the polymosphisms found in the sequence of the gene AOC1, 3 of these polymorphisms (with reference: rs1015611, rs1049742 and rs1049793) produce low enzyme activity in the metabolism of histamine.
Carriers of this polymorphism present lower DAO activity than individuals non-carriers, being the significant the differences between their enzyme activity levels. Studies indicate that these polymorphisms related to a function reduction occur with a frequency of approximately 10-13%, especially affecting middle-aged women.
Other polymorphisms of replacement of amino acids studied in the DAO gene do not show changes in its enzymatic activity. On the other hand, it has been associated with the variant p.T16M an increased risk of hypersensitivity to NSAIDS (Nonsteroidal anti-inflammatory drugs), having been proposed as a biomarker of clinical response to treatment for these drugs.