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.