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).
Keywords: Classification; Dystonia; Genetics; Next generation sequencing; Phenotype.
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