[Zonisamide treatment in myoclonus-dystonia]

Myoclonus-dystonia (DYT11) is a rare, autosomal dominant hereditary disorder clinically characterized by myoclonus and/or dystonia. The disease is most commonly caused by the mutations of the SGCE gene. Causative therapy is not available currently. Regarding symptomatic treatment, zonisamide, insulin therapy, carbamazepine and zolpidem may be utilized. If these drugs are not effective, bilateral globus pallidus internus deep brain stimulation may come into consideration. The aim of this study is to demonstrate the efficacy of zonisamide treatment in a Hungarian patient with genetically proven myoclonus-dystonia. Our 25-year-old female patient has had jerky, lightning-like movements since her childhood, mainly localized to her right upper limb. In addition, muscle cramps associated with writing and walking were also present. The symptoms were reduced by alcohol consumption. Brain MRI did not show any abnormality. Neurophysiological studies raised the possibility of subcortical myoclonus. After detailed phenotyping, genetic testing was performed, yielding the diagnosis of myoclonus-dystonia. A heterozygous mutation in the 6th exon of the SGCE gene at the position 709, resulting in an early stop codon (c.709C> T, p.Arg237*) was demonstrated. After considering the risk-benefit ratio, we decided to start zonisamide treatment. The dose was titrated gradually to 300 mg/d over 6 weeks. Myoclonus- and dystonia-specific tests demonstrated significant improvement compared to the pre-treatment status. The aim of this case report is to draw attention to this rare condition, its treatment and the importance of collaboration between medical subspecialties. Orv Hetil. 2019; 160(34): 1353-1357.