Phenylketonuria, one of the most common inherited diseases of amino acid metabolism, is caused by a defect in the phenylalanine hydroxylase (PAH) gene, and approximately 13% of the mutations affect conserved 3’ and 5’ splice sites, and are thus recognized as causing splicing defects (HGMD Professional Release 2017.1). This evidence concerns the gene PAH and glycogen storage disease VI.