Dopa-responsive infantile hypokinetic rigid syndrome due to dominant guanosine triphosphate cyclohydrolase 1 deficiency.

We report on a GTP cyclohydrolase 1 mutation-confirmed heterozygous case presenting with an infantile hypokinetic rigid syndrome and delay in attainment of motor milestones starting from the first year of life. He had a family history of dopa-responsive dystonia-parkinsonism. CSF neopterin, biopterin and HVA values were decreased.

Oral phenylalanine loading test for the diagnosis of dominant guanosine triphosphate cyclohydrolase 1 deficiency.

Objectives: To evaluate the usefulness of Phe loading test in patients for the diagnosis of guanosine triphosphate cyclohydrolase 1 deficiency (GTPCH).

Design And Methods: We studied one family composed of 13 members harbouring the Q89X mutation in the GTPCH gene, a non-related pediatric patient with GTPCH deficiency and 8 pediatric controls. 100 mg/kg of L-phenylalanine was orally administered, and blood spot samples were taken at baselines 1, 2, 4 and 6 h post-load.