Analysis of DYT1 and DYT6 in Thai patients with primary dystonia

Abstract

© 2019, ASEAN Neurological Association. All rights reserved. Background: DYT1 and DYT6 dystonias are the two most common genetic primary dystonias. However, they are rare in the Asian population and have never been reported in Thailand. DYT6 dystonia typically presents with craniosegmental dystonia with speech involvement, whereas DYT1 dystonia typically presents with lower limb dystonia, which tends to become generalized over time. Methods: Blood samples were collected from 14 patients with primary dystonia evaluated in five tertiary hospitals in Thailand. Genotyping of the TOR1A and THAP1 gene was performed. Results: Two patients were found to have a missense mutation, p.M143V (c.427A>G), in exon 3 of the THAP1 gene confirming the diagnosis of DYT6 dystonia. One patient was a woman who developed blepharospasm and lower cranial dystonia at the age of 38 years. Her dystonia spread to the neck and arm six months later. The other patient developed focal hand dystonia at the age of 34 years. The TOR1A mutation was not identified in any of these 14 patients. Conclusion: This is the first report of DYT6 dystonia in Thai patients, and the third reported case in the literature of DYT6 dystonia patients with the p.M143V variant. Our study supports the pathogenicity of the p.M143V variant in this disorder. In Thailand, DYT6 dystonia, while rare, may be more common than DYT1 dystonia. In addition, the p.M143V mutation may be common among DYT6 dystonia in Thais. Further studies with a larger number of patients may elucidate the phenotypic spectrum and reveal the true prevalence of DYT6 dystonia in Thai patients.