Sodium Oxybate-Treated Familial Myoclonus-Dystonia Syndrome Due to Novel SGCE Variant.

Myoclonus-dystonia syndrome (MDS, OMIM #159900) is an autosomal-dominant movement disorder caused by heterozygous variants in the epsilon sarcoglycan gene (SGCE) and characterized by a combination of myoclonic jerks, dystonia, and psychiatric comorbidities. Patients with MDS have a normal life expectancy with markedly reduced quality of life. Here, we report four family members diagnosed with MDS of variable severity due to a novel heterozygous splicing variant in SGCE (c.341-2A>G), including a 13-year-old female who presented with disabling dystonic spasms, myoclonic jerks, and psychiatric symptoms. She had shown little or no response to several conventional MDS treatments. However, disabling axial dystonia was significantly improved by sodium oxybate (1 g, twice daily). Although there was less effect on myoclonus, sodium oxybate treatment significantly improved the overall quality of life at the 3-years follow-up. Clinical trials are warranted to assess the clinical efficacy and safety of sodium oxybate for MDS-associated dystonia.