6-pyruvoyl-tetrahydropterin synthase (PTPS) or tetrahydrobiopterin (BH4) deficiency is the most common enzyme synthesis defect which was reported to cause of hyperphenylalaninemia. This deficiency is caused by pathogenic variant in exons and introns of 6-pyruvoyl-tetrahydropterin synthase (PTS) gene in chromosome 11q22.3-q23.3. This study is focused on the detection of DNA variants in intron 3 especially for insertion and base alteration. Methods that has been carried out in this study are DNA isolation, polymerase chain reaction (PCR), the visualization of PCR products through DNA electrophoresis, and Sanger sequencing. A total 29 variants have been characterized in this study, obtained from the DNA of one Indonesian PTPS patients and 33 healthy individuals as control. Those alterations were categorized into substitution and intronic insertion and located in the sequence of intron 3 and 4 of PTS gene. Further analyses are required to be performed to characterize the effect of identified variants to the splicing events of PTS mRNA.