Hyperphenylalaninemia (HPA) occurs in the deficiency of autosomal recessive (ar) GTPCH (OMIM: 233910), PTPS (OMIM: 261640), DHPR (OMIM: 261630) and PCD (OMIM: 264070) whereas deficiency of SR (OMIM: 612716), autosomal dominant (ad) GTPCH (OMIM: 128230) and some ar GTPCH (OMIM: 233910) are presented without HPA. 5, 6. The gene discussed is QDPR; the disease is hyperinsulinemic hypoglycemia, familial, 4.