The condition leads to insufficient production of the cofactor tetrahydrobiopterin necessary for the proper synthesis of dopamine and serotonin and for maintenance of adequate levels of phenylalanine.
[1] Biochemically, patients present with hyperphenylalaninemia, and usually have decreased levels of biopterin and neopterin in urine and in dry blood spots.
[1] According to a consensus guideline published in 2020, patients may be put on a phenylalanine-restricted diet to help bring down their elevated phenylalanine levels.
[1] To the same effect, and to normalise their production of neurotransmitters, they may be prescribed sapropterin, an artificially produced analogue of tetrahydrobiopterin.
[1] Prolonged therapy with large doses of L-DOPA may lead to the development of cerebral folate deficiency, therefore patients with decreased concentrations of 5-MTHF in their cerebrospinal fluid may be prescribed folinic acid, which efficiently penetrates the blood-cerebrospinal fluid barrier and helps restore the folate status.