Effect of tetrahydrobiopterin and 5-hydroxytryptophan on hereditary progressive dystonia with marked diurnal fluctuation: a suggestion of the serotonergic system involvement.

A daughter and her mother developed hereditary progressive dystonia with marked diurnal fluctuation (HPD) at the age of 4 and 34, respectively. L-Dopa, tetrahydrobiopterin (BH4) or 5-hydroxytryptophan (5-HTP) was orally administered to them. L-Dopa cured completely their symptoms. 5-HTP as well as BH4 improved their symptoms, especially dystonic movements. Biopterin and 5-hydroxyindoleacetic acid concentrations in CSF increased during BH4 medication. These findings suggest that the serotonergic system of the central nervous system might play some role in the pathogenesis of dystonia in HPD.