According to a systematic review study conducted in Iran, the prevalence of PAH deficiency was estimated at 93.6% (1133 out of 1210 cases), while the prevalence rates of QDPR, PTS, and PCBD1 genes were estimated at 4.1% (50 out of 1210 cases), 2.1% (26 out of 1210 cases), and 0.08% (1 out of 1210 cases) respectively. This evidence concerns the gene PCBD1 and phenylketonuria.