A Novel SGCE Nonsense Variant Associated With Marked Intrafamilial Variability in a Turkish Family With Myoclonus-Dystonia

Background: Myoclonus-Dystonia syndrome (M-D) is an autosomal-dominant movement disorder related to SGCE gene pathogenic variants. Although there can be observed variability in clinical findings, here we describe intrafamilial variability in a Turkish family with a novel nonsense SGCE pathogenic variant. Methods: A family with variable clinical symptoms resembling M-D were referred to our clinic. After preliminary diagnosis, patients were tested for mutations in the SGCE gene by Sanger sequencing. Results: Novel pathogenic heterozygous nonsense mutation in exon 3, c.272T>G; p.Leu91* (NM_003919.2) were observed in affected family members. Conclusion: Intrafamilial clinical variability, despite the same pathogenic variant described in this work, suggests that there are regulatory factors, epigenetic or environmental modifiers, which are the subject of a matter for future studies.