Enzyme: GTP cyclohydrolase I (EC 3.5.4.16)

Reaction: GTP >> Dihydroneopterin triphosphate + Formiate

DD: adGTPCH deficiency (Segawa disease)

Diagnosis: Blood, Urine, CSF, DNA
Blood: Phe (high), Neo (low), Bio (low)
Urine: Neo (low), Bio (low)
CSF: Neo (low), Bio (low), 5HIAA (low), HVA (low)
DNA: see PNDDB

Clinical signs & symptoms:
Progressive dystonia
Truncal hypotonia
Hypertonia of extremities
Hypersalivation
Choreoathetoosis
Seizures
Mental retardation

Treatment:
L-Dopa/Carbidopa (10 or 25%) <15 mg/kg/d - 3-6 doses/day
5-OH-Trp <9 mg/kg/d - 3-6 doses/day
Tetrahydrobiopterin 5-10 mg/kg/d - 2 doses/day

Alternative treatment:
Deprenyl 0.1-0.3 mg/kg/d - 3-4 doses/day
Entacapone <30 mg/kg/d - 1-2 doses