[Inherited dystonia update].
Among idiopathic dystonia, inherited dystonia whose causative gene or linkage has been clarified are named as DYT1 to DYT15. The causative genes of DYT1, 5 and 11 were identified as genes of Torsin A, GTP cyclohydrolase I, and epsilon-sarcoglycan, respectively. All three are inherited dominantly. DYT1, and DYT5 which is known as Segawa disease, are dystonia with onset in childhood. After identification of the causative gene, each disorder was found to show the various phenotypes. In both DYT1 and Segawa disease, early onset develops generalized dystonia, and later onset focal or segmental dystonia. Deep brain stimulation of globus pallidus internal segment shows remarkable effect on DYT1. Segawa disease responds markedly to L-dopa without any side effect lifelong. The pathophysiology of Segawa disease is that partial deficiency of BH4 resulted from GCH I deficiency, rate limiting enzyme of synthesis of BH4, affects the TH activity at terminal of nigrostriatal dopamine neuron. The role of Torsin A in the pathogenesis of DYT1 is unknown. For a certain neuron or neuronal system to manifest a clinical symptom, it should reach to a certain maturational level. The symptoms of inherited dystonia are influenced by the developmental level of responsible neuron or neuronal circuit.