genetic dystonia

after parkinsonism, dystonia is the movement disorder most commonly encountered in movement disorder clinics. it is defined as a syndrome of sustained muscle contractions, frequently causing twisting and repetitive movements or abnormal postures. dystonia is classified in three ways: age at onset, body distribution of abnormal movements, and etiology. the etiologic classification identifies four major categories: primary, dystonia-plus syndromes, secondary (environmental causes), and heredodegenerative diseases. known genetic causes of dystonia can be found in primary, dystonia-plus, and heredodegenerative forms. recent discoveries in dystonia genetics have led to greater ability to provide genetic testing as well hopes for better more focused therapeutic interventions. however, identified genes, such as dyt1, account for only a fraction of dystonia and mostly for early-onset forms. this article focuses on the phenotype-genotype relationships as phenotype drives gene discovery and despite phenotypic heterogeneity, it is paramount in choosing appropriate genetic tests and sometimes treatment.