Paroxysmal tremor and orofacial dyskinesia secondary to a biopterin synthesis defect.

We report a child with a systemic biopterin synthesis defect due to an absence of 6-pyruvoyl-tetrahydropterin synthase who had an unusual presentation, with three episodes of coarse "rubral-like" tremor in arms and legs orofacial dyskinesia between the ages of 3 and 6 months. Response to levodopa therapy and CSF neurotransmitter metabolite concentrations before and after therapy suggests that his clinical syndrome resulted from a secondary dopamine deficiency.