GTP cyclohydrolase deficiency

Pathology

• tetrahydrobioterin deficiency
• malfunctioning tyrosine hydroxylase, tryptophan hydroxylase
• phenylketonuria

Genetics

• autosomal recessive
• associated with defect(s) in GTP cyclohydrolase

Clinical manifestations

• psychomotor retardation
• dystonia
• convulsions
• drowsiness
• irritability
• hyperthermia
• hypersalivation
• difficulty swallowing

Laboratory

• serum phenylalanine: generally moderately elevated
• urine pteridines
• CSF 5-hydroxyindole acetic acid (5-HIAA)
• CSF homovanillic acid

Diagnostic procedures

• oral tetrahydrobiopterin-loading test (20 mg/kg)

Management

• diet: phenylalanine restriction
• pharmaceutical therapy
  • tetrahydrobiopterin
  • Sinemet
  • serotonin

More general terms

• inborn error of metabolism

Additional terms

• GTP cyclohydrolase (GTP cyclohydrolase 1, GTP dihydrolase, GTP ring-opening enzyme, GTP 8-formylhydrolase, GCH1)