This condition is very rare; approximately 600 cases have been reported worldwide. In most parts of the world, only 1% to 2% of all infants with high phenylalanine levels have this disorder. In Taiwan, about 30% of newborns with elevated levels of phenylalanine have a deficiency of THB. Subclinical deficiency can be found in individuals with poor diet (including low intake of folate or vitamin C) or genetic mutations in the MTHFR genes, which are involved in BH4 synthesis and recycling.
Tetrahydrobiopterin deficiency
Cerebral folate deficiency
Cytochrome b5 deficiency
Adenine phosphoribosyltransferase deficiency
Molybdenum cofactor deficiency
Methylenetetrahydrofolate reductase deficiency
Dihydropyrimidine dehydrogenase deficiency
Biotin deficiency