<h4>Background</h4>Tetrahydrobiopterin (BH<sub>4</sub>) deficiency caused by 6-pyruvoyl-tetrahydropterin synthase (PTPS) deficiency is a rare disorder that is one of the major causes of hyperphenylalaninemia in Taiwan.<h4>Methods</h4>In this study, we reviewed the clinical courses of 12 adolescent and adult patients (7 females and 5 males) with PTPS deficiency.<h4>Results</h4>The patients were treated shortly after diagnosis through newborn screening with a combination of BH<sub>4</sub>, levodopa/carbidopa, and 5-OH-tryptophan. This evidence concerns the gene PTS and Hyperphenylalaninemia.