Classification and genetics of dystonia.

Dystonia is a syndrome characterised by sustained muscle contractions, producing twisting, repetitive, and patterned movements, or abnormal postures. The dystonic syndromes include a large group of diseases that have been classified into various aetiological categories, such as primary, dystonia-plus, heredodegenerative, and secondary. The diverse clinical features of these disorders are reflected in the traditional clinical classification based on age at onset, distribution of symptoms, and site of onset. However, with an increased awareness of the molecular and environmental causes, the classification schemes have changed to reflect different genetic forms of dystonia. To date, at least 13 dystonic syndromes have been distinguished on a genetic basis and their loci are referred to as DYT1 to DYT13. This review focuses on the molecular and phenotypic features of the hereditary dystonias, with emphasis on recent advances.