GCH1 and Hyperphenylalaninemia: A reliable estimate of the frequency of this set of conditions is available for hyperphenylalaninemia-associated disorders, which are intercepted by neonatal screening programs for phenylketonuria (autosomal recessive DYT/PARK-GCH1, DYT/PARK-PTS, DYT/PARK-QDPR, and DNAJC12-related disorders), all including 2–3% of the overall number of patients with neonatal hyperphenylalaninemia (http://www.biopku.org/; last access 7 October 2022).