[Molecular biology of hereditary dystonia]

The causative genes of hereditary dystonia (hereditary progressive dystonia, HPD; dopa-responsive dystonia, DRD) were discovered in 1994-1995. HPD/DRD is caused by the deficiency of dopamine to less than 20% of the normal level in the nigro-striatum of the brain owing to the mutations of the dopamine synthesizing enzymes. Autosomal dominant dystonia (Segawa's disease) was found to be caused by mutations of GTP cyclohydrolase I which synthesizes tetrahydrobiopterin, the cofactor of tyrosine hydroxylase, by Ichinose et al. (Nature Genetics, 1994) in Japan. Autosomal recessive dystonia was reported to be caused by mutations of tyrosine hydroxylase by Lüdecke et al. (Human Genetics, 1995) in Germany. Hereditary dystonia, especially autosomal dominant Segawa's disease can be completely controlled by L-dopa administration. Measurement of the activity of GTP cyclohydrolase I in mononuclear blood cells is useful for the diagnosis of Segawa's disease.