Dystonia is characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive, movements. Symptoms can begin from early childhood to late adulthood, affecting a specific (focal), several (multifocal, segmental), or many parts of the body (generalized). Generalized dystonia usually consists of adolescentonset progressive and incapacitating disorders with a known genetic basis. The group of primary focal dystonia generally appears in adults and usually involves the neck, face, or arms; the number of known genes is lower, although up to 25% of cases tend to have a positive family history (Steeves et al., 2012). It is worth noting that dystonias are diseases with great phenotypic and genotypic heterogeneity, often with incomplete penetrance even within the same family (Albanese et al., 2013).
A prevalence of approximately 16 per 100,000 individuals is estimated (Steeves et al., 2012).
Although numerous risk factors have been reported in association studies, the diagnostic-genetic approach is aimed at making diagnoses with a clinical application for the patient.
To this end, four phenotypic groups have been defined :
- Isolated dystonia (primary, focal, or generalized, as the main symptom): 8-gene basic panel, with particular relevance of TOR1A (DYT1), THAP1 (DYT6), and GNAL (DYT25, adult-onset craniocervical dystonia).
- Myoclonic dystonia: specific 2-gene panel including SGCE (DYT11), whose yield is up to 50% in familial cases, and the more recently described KCTD17.
- Dystonia-parkinsonism: includes, among others, genes associated with dopa-responsive dystonia, or Segawa disease.
- Paroxysmal dystonia with other dyskinesias, which includes the PNKD, PRRT2, SLC2A1, and ECHS1 genes
All of the mentioned phenotypes are covered by our comprehensive panel for dystonia, which is indicated for an all-inclusive etiological approach and complex cases.