Genetics in dystonia.

While Hermann Oppenheim probably described the first cases of genetic (DYT1) dystonia in 1911, the 'modern history' of dystonia genetics dates back to 1994 when mutations in the GTP cyclohydrolase I gene were discovered to cause dopa-responsive dystonia. Due to the advent of next-generation sequencing, the field of dystonia genetics has been evolving very rapidly over the past two years, resulting in the reporting of 'DYT1-25' and, for the first time, in the identification of genes associated with adult-onset focal/segmental dystonia. However, three of these putative new genes still await independent confirmation (TUBB4/DYT4; CIZ1/DYT23; ANO3/DYT24) and only 11 'DYT' genes have been unequivocally demonstrated to cause different forms of dystonia. Based on a recent consensus approach, dystonias are subdivided on clinical grounds into isolated (with or without tremor) and combined (with other movement disorders) forms. Confirmed genes for isolated dystonias include TOR1A/DYT1; THAP1/DYT6; GNAL/DYT25. In the combined forms, dystonia is accompanied by parkinsonism (GCH1/DYT5a; TH/DYT5b; ATP1A3/DYT12; TAF1/DYT3) or myoclonus (SGCE/DYT11). Persistent and paroxysmal forms are distinguished according to their temporal pattern. The paroxysmal forms of dystonia/dyskinesias present with a mixed pattern of hyperkinetic movement disorders (PRRT2/DYT10; MR-1/DYT8; SLC2A1/DYT18).