[Segawa disease]

The first report of Segawa disease was a report of two girls, cousin each other, with dystonic posture, under the title of "Hereditary progressive basal ganglia disorder" in 1971. After accumulation of cases with an adult case, I confirmed this disease does not transform to Parkinson's disease in adulthood and published with a nomenclature of "Hereditary progressive dystonia with marked diurnal fluctuation" in 1976. Polysomnographical examination for evaluating the sleep effects and correlation of the natural course to the age variation of the tyrosine hydroxylase activities in the striatum, these speculated this is a particular disorder caused by non-progressive decrement of the tyrosine hydroxylase at the terminal of the nigrostriatal dopamine neuron. This was supported by PET studies in early 1990's. Evaluation of pteridine metabolites in cerebrospinal fluid revealed partial decrement of the GTP cyclohydrolase I as the cause of this disease and induced the discovery of the causative gene. After the discovery of the gene, an autopsied case with dopa-responsive dystonia was confirmed as Segawa disease and the neuropathological and histochemical findings confirmed the hypothesis. Furthermore, these showed rather selective involvement the D1-direct pathways in the disease. However, it was also clarified existence of two types, one, classic type, postural dystonia and the other action dystonia with vigorous dystonic movements besides dystonic posture, which, is postulated to be caused by the dopamine neuron innervating to the subthalamic nucleus with D1 neuron. Existence of these two phenotypes also provides phenotypical variation of Segawa disease.