L-dopa-responsive infantile hypokinetic rigid parkinsonism due to tyrosine hydroxylase deficiency.

Tyrosine hydroxylase deficiency was confirmed biochemically and genetically in four unrelated Dutch patients. The patients have a hypokinetic-rigid parkinsonian syndrome with symptoms in early infancy (3 to 6 months of age). Only sporadic dystonic movements were seen. There was no diurnal fluctuation. All patients showed a rapid favorable response to low-dose L-dopa/carbidopa treatment. Motor performance improved but did not fully normalize. The patients have mild mental retardation.

A review of biochemical and molecular genetic aspects of tyrosine hydroxylase deficiency including a novel mutation (291delC).

An overview is given of the current knowledge on the human tyrosine hydroxylase gene and on the biochemical aspects of diagnosing defects in this gene. Diagnostic biochemical findings are described in four cases of genetically confirmed tyrosine hydroxylase deficiency. Decreased CSF levels of homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG), together with normal pterin and CSF tyrosine and 5-hydroxyindoleacetic acid (5-HIAA) concentrations are the diagnostic hallmarks of tyrosine hydroxylase deficiency. At the metabolite level the diagnosis can only be made reliably in CSF. Strict adherence to a standardized lumbar puncture protocol and adequate reference values are essential for diagnosis of this 'new' treatable neurometabolic disorder. Measurements of HVA, vanillylmandelic acid (VMA) or catecholamines in urine are not relevant for diagnosing tyrosine hydroxylase deficiency. The diagnosis should be considered in all children with unexplained hypokinesia and other extrapyramidal symptoms. Three of our patients are homozygous for a mutation in exon 6 (698G > A) of the tyrosine hydroxylase gene and one patient was compound heterozygous for the same mutation and a novel truncating mutation in exon 3 (291delC).